A Republican in the White House would mean no Oil Embargo against Japan, so they have no reason to go to war with the US, and an isolationalist president would certainly go out of his way to avoid them having any reason to go to war. So trade would continue.
Don't be so sure. A Republican, being pro-business (unless I'm wrong...) would be very disinclined to allow Japan to potentially deny the U.S. access to the biggest consumer market in the world, Sinophile or no Sinophile. The total embargo might not happen (& BTW, FDR didn't intend it to be total), but it would probably still happen. In fact, with less invested in trying to get into war with Germany (which was, despite the Pearl Harbor conspiracy loons' claims, FDR's main objective), a GOP Pres might be more inclined to tell Japan where to get off...& we're back to Hitler being a maniac & pulling the 2d most ill-advised DoW of the century (after attacking Pearl Harbor).
Japan...still probably go South.
Did you not read what I said about seperability? Absent knowing the IJA-IJN interservice issues, saying what would happen with any confidence is up there with picking a date for Hitler winning the war, or naming H.P. Lovecraft President.
Breaking Australia and New Zealand from the British Empire would be much more productive.

Do you honestly expect them to surrender to Japan, or what? And how, exactly, will Japan achieve this?
A Republican President means no Lend-Lease. Britain...probably can't sustain the the war effort much longer without help.
OK, so what does HMG
do about it? Scale back the bomber offensive? Cancel it? Ask Free France for more help? (There were still colonial territories...) Ask for greater efforts from Canada, Oz, NZ, India, SAfr? (I confess, I don't know how close to their financial, production, or manpower limits they were.)
Now, Japan will stay out of the war, as per their neutrality pact
and a slice of Eastern Russia for Japan could happen
I'd love to see your explanation for how those 2 mutually contradictory outcomes can happen.
China, Australia and India are enough to keep the island empire busy.
Do I take from that you believe Japan was going to
invade Australia? LOL. ASB. IJA had neither the manpower nor the shipping to attempt it in their wildest dreams.
has to get his army across the Volga, which is held by the Red Army.
Uh, it's only, what, 40mi away? That's about a week's advance. Given Red Army hasn't the MT to counteratack & trap von Paulus, which prewar MT production might still allow.
negotiated peace. If he's actually capable of doing this.
I deeply doubt it. And considering how brutal the Germans were to the Russians, I'm equally doubtful Stalin would agree before Hell was colder than Novosibirsk. He might lose, but he wouldn't quit. I have a hunch most Russians would have agreed with him: better to die on our feet than live in chains. So long as Russia is fighting, Britain has some chance of Hitler making a stupid decision & DoW the U.S. Presuming he hasn't already, over Japan...
Spain would probably get Gibraltar.
When did Spain join the Axis?
in exchange for Australia and New Zealand's independence.
"independence"? When did the Klingons arrive to help IJA with the conquest? "He's dead, Jim."
India and Pakastan may remain British for a time
Uhhh, it's Pak
istan. And Pak
istan didn't even
exist yet...