The USSR remains gigantic, with tremendous strategic depth, and an infrastructure of factories and refineries set up in defiance of capitalist logic but quite strategically sound east of the Urals.
Germany and Poland, even with the Baltic states (and probably not Finland) glommed onto the bandwagon, remain far less comprehensively capable of autarky than Hitler's Reich as of 1941 OTL, with far less manpower.
It is just absurd to me people think the Reich has a snowball's chance in hell in the long run. In the short run, sure maybe they can do say half as well as OTL Barbarossa.
The Soviet Union does not require Lend Lease from anyone, does not require anyone bomb the Germans from the west (Poland and the Baltics are way out of bombing range from Britain or France anyway). They will absorb the blow, hold it, and come back to grind the Reich and its allies into fine powder. Questions of whether the Anglo-French Entente, clothed in the tatters of the League of Nations or just nakedly operating on their direct imperial power, will actually side with the Axis and in effect join it are relevant to whether the Reich can even survive--but I think domestic politics in the two satisfied imperiums will block active aid on more than a private basis to the Reich.
As for Romania being "sure" to trade oil to the Germans and hence Poles...for what, exactly? I think it is quite possible that the Romanians will instead look at the Soviet colossus, think twice and thrice, and seek Anglo-French Entente support instead, and sit it out arming themselves as best they can.
The USA might be unlikely to enter the war on anyone' side...but US industry will be keen to sell products to those who can pay, which is to say mainly the Entente.
With POD as late as 1939, there is no reason to doubt both France and Britain have awoken from their interwar slumber, when official British policy was that "no major war will occur for a decade," with the starting point of the "decade" moving forward constantly through the 1920s and early '30s, and also it was assumed the adversary would then be--France! But by the time of the OTL Czechoslovakia crisis, both Britain and France were seriously rearming again--Chamberlain just felt that Britain had not been at it long enough to risk a war with Germany--in 1938. I do suppose he sincerely thought the Munich Accord dismembering that poor country (but not giving the remnant of Czechia to the Reich outright--that seizure was a violation of the Accord) had in fact satisfied Hitler and bought "peace in our time," and if Hitler had in fact as the joke goes "met a nice Jewish girl and settled down" the Entente rearmament would have slacked off.
But not right away! Globally, the whole world, even the Entente empires (and the smaller fry imperialists, Netherlands and Belgium) which had control of their colonial empires to buffer things were still knocked flat and reeling from the 1929 Crash. Basically the nature of the great crisis was that private investors had been burned badly. It was not that they had no capital to reinvest and get the industrial wheels turning and the engine of production firing on all cylinders again--it was rather that they lacked confidence anyone would be in a position to buy the products of full production again, and the investments would give a poor or even negative return, again. So the surviving capitalist fat was sat on, not invested, and workers went desperately hungry unless fed by state dole. Most people had jobs, sort of, but poorly paid, and the number of people with zero regular employment made them a serious political bloc one way or another--the usual depression of such people blaming themselves did not apply, anyone could see the larger system had failed and it was not the fault of a person on hard times probably that they were so desperate.
In this context, preparation for war was a pure win, economically speaking. The finance to pay for the cost of the materiel and feeding expanded armies and navies was there, it just needed to be ferreted out of rich hands. It is actually to the credit of the liberal powers they did not mobilize to go to fratricidal war with each other in the face of war as the obvious solution. This is more or less exactly what Japan was doing of course, from quite early in the Depression. The impression Germans and foreigners got that fascism worked depended in great part on Mussolini and Hitler driving the march to war by commanding the finance to get the munitions works going and thus bootstrap the entire civil economy back up again--though Italy having late acquired and largely useless colonies (apparently Libyan oil was not discovered yet) and Germany having no colonies whatsoever, both were tightly constrained by limited domestic resources.
But spurred into buildup by the threat of the rising Reich, Britain and France both stood to gain domestically by buildup. In milder form than the quid pro quo that mollified Italian and German wealth owners, the stagnated monied classes of Western Europe would clearly be reaping back most or even more than the money taxed away from them when their factories started churning out munitions, along with other lines of business now catering to a much more effective demand as arms factory workers at last had reliable paychecks to purchase their vital needs with and perhaps start buying some long deferred optional purchases too.
Men conscripted or otherwise recruited into the military of course are no longer on the dole or unemployment lines; they aren't much of a consumer market but they are being fed and issued uniforms which represents serious demand in itself. Their families might suffer on their meager pay, of course the tendency is to draft the young first--but "paradoxically" (if one still has a naive faith in the rationality of capitalism anyway--it has rationality all right, just not the humane one most of us have been propagandized to believe in) during the Depression, at the very time the traditional male wage worker had the toughest time finding work, women were employed (at even lower wages of course) in droves. This is one of the things the Nazis promised to "free" Germany from, the propaganda was that women could go ahead and marry their boyfriends already because the Aryan order would make sure their men had jobs. Well, they did have jobs, and they were taking home bigger paychecks--at lower hourly wages than before the Depression set in; higher incomes were mainly from working lots of overtime. But the women did not lose their jobs (nor could the families, promises notwithstanding, afford for them to quit)--they did however get married. The Nazis basically wound up making it respectable, or anyway normal, for both parents to work.
So rising military recruitments did not mean starving families because the women had to step in to take the emerging jobs anyway.
So had Hitler behaved and satisfied himself with ruling all the Germans (well, there were always more, in pockets here and there throughout eastern Europe actually) I suppose the surge in British and French arms would have slacked off, but not instantly.
As things are instead, both OTL and here, with Germany clearly actually meaning it about going to war just like it said in Mein Kampf, clearly the need for both imperial powers (and the Dutch, dunno about Belgium, I am not aware of any remarkable Belgian weapons systems built in the later '30s, but the Dutch had quite innovative works going, making highly advanced submarines and of course the Fokker firm making pretty good aircraft) to actually have arms and men on hand kept the arms based recovery going without any political stopping point.
The USA would not sit this out. OTL, looking at the monster the Reich had become, the French and British felt they had maxed out their self-arming capacity already, and turned to the USA for major purposes of weapons systems as well as stuff like grain and other food. With no U-boats preying on them (OTL, Hitler refused to allow a major buildup of U-boats before the war, hoping to sweet talk the British into standing aside; without a DOW between the powers either he prudently continues to avoid provoking the British, or, believing that wartime controlled Germany is opaque enough to get away with anything, authorizes them belatedly--but British intelligence was quite good and they'd know about it, which would turn more British leading opinion against the notion of working with the Reich and more toward eventual war being in the cards) trade with the USA has no hazards and no impediments, and the American private actors would be quite keen to supply the market. America Firsters would be sounding the alarm against a repeat of US involvement in the Great War and against financing the Entente, but the Entente is not actually at war yet and can afford to just buy what they can afford year to year, and both FDR and a substantial US bloc of capitalists would be in favor of aiding the Entente offsetting the AF lobby.
Giving the Soviets Lend Lease is probably a political stinker FDR would avoid, but more subtle good offices, permitting the Soviets to purchase stuff on the private market without restriction, diplomatic support--this sort of stuff I think the administration could get away with and FDR still be reelected handily in 1940. Perhaps all these latter day Axis fanbois I see coming out of the woodwork here forget just how popular FDR was, how beloved the New Deal was, how many American voters feared the return of the Republicans they perceived (with great justice, IMHO) had dropped the ball so spectacularly in the onset of the Depression and left the American working people twisting in the wind, with stuff like the shooting of the Bonus Marchers still quite current in their minds.
In reality, US recovery was happening in the late '30s, and, as a humanist I say sadly, mainly due to the buildup of war and preparation for war. But as noted, partial militarization of the USA would be domestically OK certainly under the rubric of "preparation" and "armed neutrality." As things were the consensus for the USN being "second to none" had prevailed for generations by this point, and behold the RN, the main benchmark of comparison, is perforce building up; the IJN is an objective threat; even the French navy is becoming a major thing. Add to this the quite fashionable notion that air power is the new key to success, again shown here in fanboyism about the alleged effectiveness of OTL Western allied bombing campaigns; building up US air power is quite politically fashionable at this point.
The USA may not actually enter the war, assuming the Japanese are distracted. But aside from the fact that Japan would still need resources from the tropics they simply cannot get in conquests from the maritime Soviet Union, and can obtain only by either purchasing them or by seizing their sources, I also think that the notion the USSR is a paper tiger is even more absurd on the Pacific front than in Europe. With the Soviets distracted by a fight for their lives in the far west, the Soviet far east might be scanted of priority and therefore the Japanese might temporarily enjoy successes they did not OTL...but eventually the western front will stabilize, Soviet industry and recruitment and military competence will shake down, and reinforcements will come east to take back any losses, and double down on the OTL support of the Chinese and direct front line steamrollering the Japanese on land. Indeed as OTL, the Soviets might find a de facto truce with Japan advantageous--but only on the terms of dislodging Japan from any ill gotten gains. Certainly the "northern strategy" is a flash in the pan here and Japan's warlords will face a dire situation all the more starkly. A strike southward seems inevitable to me, that or the collapse of the Japanese rule by the army. But the literally gung-ho Japanese army lobby sees no reason, and is willing to assassinate any opposition; on paper the Emperor is inviolate but first of all there is ample reason to doubt Hirohito's good sense, and second--I don't think even an Emperor's firm will will override the banzai spirit of these middle officer types. If he were allowed to issue a firm stand down order, as after Nagasaki OTL, that is one thing, but I think he might turn up tragically dead, no doubt killed by wicked foreigners, before being allowed to issue such an order should it seem vital to him to attempt to do so.
The reason it is more insane than OTL for them to strike south at the DEI and other targets held by European imperialists seems obvious enough; if the Entente is not embroiled in full on war with Hitler in Europe, they can clearly give a lot more attention to defending their possessions in southeast Asia. I honestly cannot decide if that would deter them from a banzai attack or if they'd do it anyway, reasoning as OTL that victory is a matter of spirit, and the liberal powers were fatally mired in soft corruption and would seek a cowardly peace. Would they carefully avoid at least pissing off the USA? Well, we were their chief potential adversary as the USN perceived them to be theirs, and it was American actions that drove what infuriated the Japanese ruling cliques the most. It was reasoned or rationalized that striking just at the European holdings and bypassing Yankee held Philippines would be a big mistake as the Americans could decide to enter the war against them any time and cut communications southward, unless the Philippines were decisively neutralized up front.
So US involvement in war in the Pacific at least seems quite likely, and if Japan has in fact been lured into joining the general pile on against the USSR, there is FDR's excuse for formally allying with the Soviet Union right there. It probably would not justify Lend Lease on anything like the OTL scale, but giving the Soviets some critical resources would seem quite a smart move diplomatically and strategically at that point. Again I don't think the Soviets actually need it if Hitler is foolish enough to attack the Soviets before securing France and the Low Countries. Sure, there might be a big bandwagon of southeastern European nations, the Romanians might foolishly join, and for a time, maybe a year, it might seem that the Axis led crusade against the Bolsheviks is going swimmingly. But when the tide turns, and it will, this just spells doom for all these countries in the longer run.
But a small scale of US Lend Lease under the rubric of an alliance strictly against Japan can catalyze this Soviet steamroller victory a lot sooner than I otherwise might grant it would be delayed to.
If FDR lives no longer than OTL, he might still be elected to a fourth term and see the Reich collapsing, Poland having already gone under Red Army tank treads. If Romania is fooled into joining, they'd be subjugated by this point too and the main thing delaying Red Army conquest of all southeast Europe would be their decision to concentrate force in the north to break Reich resistance.
I can conceive of an end game other than Red tanks pushing to the Rhine and pouring into Italy, but it would involve a major anti-Hitler coup in Germany being first of all improbably successful, and then accepting terms of surrender that might protect the personal hides and privileges of the coup artists, but leave Germany under close and permanent Soviet supervision. Conceivably American good offices might negotiate a compromise subjugation where Germany much trimmed back and possibly balkanized is demilitarized with both Entente and Soviet officials swarming the place to monitor it, perhaps with some Americans to keep an eye on both and serve as referees, with it quite understood that the Soviets will not be allowed to turn Germany into a militarizing arsenal for themselves, but that otherwise the Soviets as victors get primary say in final resolutions of issues. Stalin or likely alternates to Stalin will be cynical enough to not insist all Communists be rewarded, but handpicked reliable ones sure to follow orders will flock back into Germany (the ones who managed to survive underground will not be deemed so trustworthy!) to issue orders to their puppet Junkers and industrialists; Germany might be prevented from being turned into a "worker's state" and perhaps nothing resembling democracy really ever restored, elections being a choreographed pre-agreed to show "contest" resulting in pre-selected balances of conservative and Communist approved candidates who say just what the script tells them to in the Reichstag (or Bundestag, or -stags of the various balkanized pieces). East of Germany it will be a Soviet run show top to bottom, I daresay the USSR will not annex a lot more than OTL but will install reliable puppet governments.
Basically the outcome is the Warsaw Pact reaches a lot farther west, perhaps just maybe if the USA does get entangled in a fairly friendly way with the Soviet war effort, with Germany neutralized instead of split between two blocs.
Finland, I am with Michele on this, would not get into war in the first place, and again perhaps US good offices can keep it that way, negotiating the Finns giving the Russians some important concessions in return for their borders not being adjusted and retaining meaningful autonomy and freedom, albeit as OTL with a nervous eye toward not antagonizing the Soviets.
I gave some thought to the notion that the early Great Crusade period of German success might seduce Turkey to the Axis side, which would open up the Black Sea to invading Italian ships if the Entente allows this, but given how carefully Ataturk stayed on the fence OTL, I think that is the most reasonable thing to expect here too.
I also wonder, all this "oh the Soviets collapse and the Axis wins!" gushing, did anyone notice that this nerfed Barbarossa would be happening later in the year than the OTL ultimate debacle started? As things were, Hitler wanted to attack a month earlier in 1941, but got distracted by needing to come bail Mussolini's misadventures in the Balkans out. Granting the OP was flexible and did not commit the attack to being as late as September, what with settling the status of Czechia as a conquest, I think it must start later in the year.
I would think facing the onset of winter predictably before he would reasonably expect the job to be done, Hitler would do better to delay all this risk until spring of 1940, buying more time to build up, maybe test out the new built Reich forces in the Balkans to get those southern regimes into line.