The elephant in the room everyone's talking around is how, exactly, do the Nazis defeat and occupy the United States? The nature of the resistance is going to depend heavily on how the conflict goes, beyond that there's little point in discussing how the occupation would go. Clearly a France-like defeat is going to be highly unlikely and if the Nazis are trying to invade the United States they'd be doing it long after the British Empire and the USSR have been totally subdued and their colonies at the minimum neutralized as a threat. On top of that you'd have a US government that, barring paint smoothies becoming a thing, would be taking steps to secure the Western Hemisphere and prepare their defenses for warding off any and all Axis attempts to invade the Americas.
Alongside this is the enormous amount of material, preparation, and time it would take to prepare for launching an invasion of the United States. For a point of comparison the US needed a solid two years, with the largest industrial output on the planet, no Eastern Front demanding constant reinforcement, or a snowball's chance of enemy naval forces staging a raid serious enough to disrupt production, to produce the necessary ships, especially fleet oilers, and specialized equipment to support the thrust across the Pacific. What this means is the US will have more than sufficient warning of any intended Nazi invasion and have ample time to prepare for it.
Then there's the question of what Nazi Germany will be looking like. Odds are if they've beaten Britain and the USSR they're implementing Generalplan Ost which called for a level of mass genocide that is without precedent in human history. Killing hundreds of millions of people takes a lot of work, weapons, and material to do so it would be safe to assume the first couple of decades following the end of the war they won't have the resources to crush European Russia into dust and prepare adequate forces for an invasion of the US. Especially if you have a US that would be receiving British refugees and probably a handful of Soviet and Jewish ones too with their own horror stories to tell.
What that means is by the time the Nazis actually have the means to even try this you'll be looking at two massively mobilized continental power blocs squaring off for war. Nukes are unlikely on the Nazi side (thanks to their wholehearted embrace of boneheaded ideas like Deutchphysik) but even without them you can expect other WMDs to be in play. You'd be talking a conflict that would be best summed up as the Pacific War (for the sea phase) followed by the Eastern Front and China (for the land phase) on steroids, a struggle that would make CalBear's already massive and horrific Anglo-American Nazi War look like a playground scuffle. It would be unbelievably bloody, incredibly destructive, and even in victory the Nazis would be left limping in pain from the cost in blood and treasure. You won't be getting anything like the relatively placid Berlin of Turtledove's In the Presence of Mine Enemies and probably much more like a post-apocalyptic hellhole on all sides.
In any world where they have subdued to outright conquered the USSR and British Empire you are assuming a level of competence among the Nazi leadership that Hitler, Himmer and Göring simply did not possess or the British and Soviet leadership eating lead pain chips, likely it would have to be some combination of the two.
Either way I do think the Germans would have nukes by the 50s as they would have absorbed many of the scientists, spy networks, and intelligence from Britain and the Soviet Union.