There was a similar thread about this a few months ago here

I'll copy my answer below:

As far as I know, there has never been a serious plan by any nation for the invasion and occupation of the mainland US. In both World Wars Germany (and in WWII Japan) limited their warplans to establishing naval supremacy and possibly bombarding coastal cities. I don't think the USSR had a plan to occupy the US, just as the US did not have a plan for the occupation of Russia (at least, I think they didn't, I'd be happy to discover otherwise).

The closest I can come up with is a speculative plan commissioned by Kaiser Wilhelm in the early 1900s, which would have included an occupation of some North Eastern cities such as New York, and a march to DC in order to force the US into a peace favourable to Germany. The occupations would be very short term so I don't think they accounted for a militia forming. The entirety of the general staff thought it was a ridiculous idea and only made the plan because the Kaiser ordered them to. This information came from http://www.zeit.de/2002/20/In_New_York_wird_die_groesste_Panik_ausbrechen My German is nitch sehr gut so I couldn't go into much detail, sorry about that.

This is about as close as I could find to a serious proposal to invade the US. As far as I know, no others exist, and honestly I would be extremely surprised if they did. I know this wasn't the answer you were looking for, but I hope it was at least informative.

I've had to remove quite a lot of posts already and I will continue to do so.

Please stop writing if you are not entirely certain what you're writing about. We do not allow speculation, guesswork or faint memories from something you read a few years back.

Also, please stop referring to the Zimmerman telegram as something that occurred during WWII. It happened during WWI and was one of the reasons for the entry of the US into the First World War in 1917.

Finally, please stop recommending fictional books.

Check out Adam Tooze's Wages of Destruction, especially the earlier chapters on Nazi ideology and its adaptation and reshaping of the earlier Wiemar and Imperial political economy. Basically, the Nazis saw Germany placed in opposition to other strong-willed national competitors. The immediate competitor was seen in Great Britain, but it was never really treated as a long-term threat since, by the 1930s, one could see the US supplanting the collapsing empire. Strength of will and blood purity were the boons that the German people could rely on, but that would be expressed through economic production.

The German people were not in a position to compete with the growing industrial power of America, especially since the NSDAP inherited the collapsing agriculture of earlier German governments, but it was never about directly invading the US. There was an ideological transformation of the earlier Imperial and Weimar need to expand colonially. Imperial Germany was shut out of the global south and lost what it had in the first war, so seizing eastern Europe from the Russians was a means of expanding territorially and capturing a colonial population that home markets could export to (19th century imperialism 101) -- however, the Nazis just wanted the land to expand agriculturally and to grow a strong German population (necessary to compete with large populations like those in America and China, and to feed the industrial machine). That's Lebensraum. The later invasion of the Soviet Union was also an ideological necessity to crush socialism, and a material one: before the invasion of Poland, the leadership of the German military assessed oil reserves at around five years, and the only significantly developed oilfields in the world were in Texas and Baku.

So tldr, the Nazis weren't interested in invading America and seizing it. Nazi ideology saw a longer struggle involving those it saw as strong industrial nationalist competitors, chief among these the United States (but also others like China and Japan). The militarism inherent to Nazi policy would have meant war, absolutely, but we're talking about a global war after decades of cold war arms racing and rapid industrialization. The attacks during the war were aimed at short-term industrial and logistic disruption, including some speculation at bombing America itself that they were never in a position to entertain.

Like I said, this is in Tooze and he goes into it way better than I do.

I'm watching about Churchill sinking French ships, and if Britain falls, US plans for Nazi invasion and I'm curious how realistic it really was

It wasn't at all. Essentially the only way Germany becomes a significant threat to North America is if you wave a magic wand and the entire RN falls into the hands of the Germans, and the Germans are able to man and supply it. Since the best way to have "Britain fall" is to wave a magic wand and take the RN off the table...the Germans are never going to have the naval superiority to clear off the USN(the USN was already pegged to the largest navy in the world through the Navy Treaty system, and after it expired the USN went on a naval procurement spree that culminated in the Two-Ocean Navy Act. One should note that this act was passed a year and a half before Pearl Harbor(right after the fall of France), and the number of large fleet carriers ordered dwarfed number of Battleships and ersatz-battlecruisers.

The disparity of force against the Kriegsmarine is massive, and given that half of the troops used int he African landings(from A Army at Dawn) sailed straight from Norfolk, Virginia, the US almost certainly hs the logistical reach to invade territory/establish bases very close to continental Europe. Germany has no such ability.

Did the Nazis plan on taking a South American country as a jumping off point?

It would be difficult to imagine a scenario where the US would let it get to that point. No South American country was so friendly with the Axis that they essentially joined it even when it seemed as if Germany was unstoppable, in part due to the immense political pressure the US brought.