A problem with Nazi Germany v. America Cold Wars is that unlike Communism Nazism isn't an ideology that can gain support from everyone regardless of what continent they reside in as it is a racial ideology to the core. All such a Cold War would consist of is the Nazis and Italians engaging in brutality to get the colonies of Vichy France, Spain, Portugal, Italy etc. in Africa and eventually running out of money before collapsing in the 60s or 70s. Not to mention the Slavic insurgency in Eastern Europe. It wouldn't be the worldwide global struggle as the OTL Cold War was.
I think it's an "either or situation", after putting a lot of thought in it over the last year.
For one,
given people like Nasser and Saddat did in their youth dabble in Nazi organizations/thinking, I don't think there's a lot of merit to claim Nazism wouldn't have any appeal in the Third World. It also doesn't need to be genuine belief anymore than it was IOTL Cold War; both sides then were more than willing to fund just about anybody against the other, and I still see that pragmatism existing here. For what it's worth,
Hitler's thought process in the last half of the war very much seemed to signal either a changed opinion or his original stance coming to the fore in his final days:
"The white races did, of course, give some things to the natives, and they were the worst gifts that they could possibly have made, those plagues of our own modern world-materialism, fanaticism, alcoholism and syphilis. For the rest, since these peoples possessed qualities of their own which were superior to anything we could offer them, they have remained essentially unchanged. Where imposition by force was attempted, the results were even more disastrous, and common sense, realizing the futility of such measures, should preclude any recourse to their introduction. One solitary success must be conceded to the colonizers: everywhere they have succeeded in arousing hatred, a hatred that urges these peoples, awakened from their slumbers by us, to rise and drive us out. Indeed, it looks almost as though they had awakened solely and simply for that purpose! Can anyone assert that colonization has increased the number of Christians in the world? Where are those conversions en masse which mark the success of Islam? Here and there one finds isolated islets of Christians, Christians in name, that is, rather than by conviction; and that is the sum total of the successes of this magnificent Christian religion, the guardian of supreme Truth! Taking everything into consideration, Europe's policy of colonization has ended in a complete failure."
And further:
"Never, at any price, should we have put our money on France and against the peoples subjected to her yoke. On the contrary, we should have helped them to achieve their liberty and, if necessary, should have goaded them into doing so. There was nothing to stop us in 1940 from making a gesture of this sort in the Near East and in North Africa. In actual fact our diplomats instead set about the task of consolidating French power, not only in Syria, but in Tunis, in Algeria and Morocco as well. Our 'gentlemen' obviously preferred to maintain cordial relations with distinguished Frenchmen, rather than with a lot of hirsute revolutionaries, with a chorus of musical comedy officers, whose one idea was to cheat us, rather than with the Arabs, who would have been loyal partners for us."
Now,
this isn't defending Hitler as some sort of Anti-Colonial hero, but I do think it shows that blanket statements about the colonial struggle in the event of a Nazi-American War aren't really valid, as even Hitler had the capacity to at least cognitively grasp pragmatism on the subject. You can also expand that into another area: If the Nazis control the European homelands, what does American Anti-Colonialism mean for their the Free French/Belgian/Dutch/etc allies?
If you, as the Americans, start supporting Algerian independence that leaves not only the Free French angry with you, it also serves to improve the legitimacy of Vichy by giving them free propaganda to use against you as well as the fact you're effectively destroying the Free French as a movement by removing their main resource base. Same goes for the British, because it threatens to destroy their economy; IOTL, London had the choice between the Commonwealth and joining Europe. If you don't want them to join Nazi Europe, you have to let them keep the Empire in some shape or form, which then leaves you exposed to the Nazis to agitate against you. One conclusion I've come to is if the Americans do go Anti-Colonial and Britain loses her Empire, at a certain point you're going to get your TTL's version of the "Nixon goes to China" moment with Nazi Germany simply because high defense spending and no ability to trade is going to crash (America is still going to become dominant even with the Dominions) the British standard of living.