Of course it is--relatively. Absolutely, I don't believe Stalin, who clearly has control over the Spanish regime, is going to order a Red Bloc strike against the bourgeois powers--nor will the four powers attack Spain, Czechoslovakia or the USSR. On paper, as a Bolshevik, Stalin is supposed to be actively working to destroy bourgeois power, but two things rein him in.
On the abstract level, Bolshevism certainly is a declaration of war against capitalist order...but it also emphasizes that it is the common people of this or that nation who are expected to rise up and defeat their own capitalists. This is of course not what happened in either Spain or Czechoslovakia! In both cases it was actually a case of Red Army presence escalating to commanding levels, giving cover for NKVD purging and manipulations. At least that is what happened in Spain--it does seem to me that when CZ goes Red, they will do so by democratic vote. And it remains to be seen whether Stalin will have the sort of autocratic power he does by this point have in both USSR and Spain. So--the Soviet Union, by Leninist doctrine, is always at war with the capitalist powers great and small, and must expect to be brutally and heavily attacked. But it is ambiguous in terms of that doctrine whether the Soviet state has any obligation to make war on behalf of a people who have not effectively challenged the legitimacy of their bourgeois governments themselves first. If it is convenient to claim this, in some opportunistic instance, then yes the Red Army can surge across the border and conquer a neighbor. But vice versa if it is not convenient, and serious and heavy war seems a likely consequence of such an intervention, then any Communist is on solid ground saying the "correlation of forces" is adverse and that it is after all the responsibility of the proletariat of each nation to rise up, and that if they can do this then the USSR is obliged to back them up as ally and patron. And not before!
More pragmatically, Stalin has reason to worry about some military leader becoming very popular due to battlefield success, and couping himself out as a Napoleon expy. Thus, his OTL policy of raising up a massive Red Army, and then not ordering it on any offensives until after Hitler struck at him and sent the whole force reeling. Well of course not zero--certainly they attacked Finland, and Poland, and took over the Baltic Republics by force and extorted concessions from Romania. But all of these actions were under cover of the Hitler-Stalin Pact. Without that in place, we have no reason to think Stalin will order any offensives--except in the sense of intervening in a civil war, as in Spain.
So--in real life, I don't believe either side will attack the other. But certainly if a civil war were to break out in France, Red Spain would be a base from which the Soviets would project material power to aid (and attempt to seize control of) the left faction.
And while I am quite certain Stalin will not in fact order the first blow, I suppose there are lots of political leaders and mass numbers of voters in such nations as France, the UK, still more in Germany, as well as many smaller nations, who assume the Reds will in fact attack at some point, and are very keen to advocate military preparedness against this at least, and in some cases will be preaching a preemptive strike against the Reds--if not so foolhardy as to strike at the Soviet Union itself, then perhaps quite gung ho for "liberation" of Spain today, and Czechoslovakia tomorrow.
Now compare this to Franco OTL. During WWII, which might be the period your comment is limited to, Franco had strong ties to the Axis--yet he procrastinated and temporized and ultimately managed to avoid being tagged as an Axis state. (Quite aside from crediting Franco with any serious regard for the interests of Spaniards generally, which I suppose he had in some limited and conditional sense, it was only pragmatic for him not to let himself be unambiguously tagged as a puppet of Hitler's. Had he done so, and let Hitler have his way in all things, he himself it seems likely to me would be couped out one fine day in favor of someone more amenable to taking Hitler's orders. And meanwhile, the Allies would damn him as another Quisling and tighten up the blockade, and take control of most of Spain's colonies, ultimately all of them; Spain would probably not get them back. Especially if Spain were not invaded and conquered and Franco survived to negotiate terms with the Allies. Spain was deeply dependent on imports which Allied blockades limited but did not choke off; being branded an Axis member would hurt Spain terribly even if neither side actually fought there.
Then after the war, Franco (except insofar as we bracket him and Portugal's Salazar as essentially two of a kind) was absolutely alone if they wanted to identify as a "fascist" power. I think yeah, Franco was surely a fascist, but it was not in the interest of the Allies (except possibly the Soviets, but they had other fish to fry) to take the position they were that. With no strong fascist power to ally with, in cold blooded realpolitik terms Spain was no threat, and once the rift between Soviets and the rest of the western Allies solidified, Franco was actually courted as a reliable anti-Communist. Eventually there were American bases there and long before Franco died, Spain was formally in NATO.
So you can't draw any meaningful parallel between Francoist Spain and TTL's Red Spain, certainly not after 1945 OTL. With Hitler's collapse, opposition to Franco outside Spain was a purely political position. Plenty of Americans or Britons or French people could despise him as a fascist, and rightly so IMHO--I'm one of these western leftists you see. But their national governments had no quarrel with him and no fear of his regime as any kind of threat to anyone but perhaps, in sentimental moments of reflection, his own national subjects. But no Western NATO nation made an issue of it as a matter of formal policy. Certainly not Uncle Sam.
Red Spain on the other hand is going to be seen as a dangerous front of Soviet power; the only thing that can mitigate the perception (at the level of national policy, if not the mythic public opinion of each nation's citizens, which will be divided in fact, no nation is ever of one mind!) that Spain is an enemy would be if some of these nations were to find it convenient or necessary to ally with the Soviet bloc. Which doesn't seem likely to happen any time soon.
Can Stalinist control lead to Spain developing its potentials to become a serious threat in its own right? I doubt it, I doubt Spain has the population even if ruthless Stalinist industrialization policies cause the abstract per capita material wealth of Spain to increase considerably. And realistically Stalinist development will create liabilities even as it also leverages assets into being. As a leftist of strongly socialist views, I believe in principle an anti-propertarian, anti-market, socialist regime might be able to prosper on all fronts--though I can't point to any successful examples. Specifically Stalinist policy will be a mixed bag in outcomes, that is I fear all too certain.
Spain's objective threat is limited then, and is mainly serious insofar as the Soviets can project power there, setting up bases for planes and ships and masses of men. If it comes to open war, the Western powers, even with Germany sitting it out, have ample power to cut Spain off and thus create great hardship there and probably greatly stifle whatever material productivity the Stalinist planners can foster. Again, this is without taking a step in the direction of actually invading to intervene.
If a situation arises where Spain is invaded, I suppose the collapse of the Stalinist Red state there is inevitable. But I also think such invaders and any conservative Spanish who ally with such invaders will face a really ugly and tough insurgency. It would be no cheap victory.
And such a piecemeal rollback of Red power could in fact trigger general war with the Soviets.
But since Western leaders are mostly going to assume Stalin intends to attack somewhere or other some day soon, Spain will trouble them as a costly threat as long as such tensions exist.
