the "plan" of nazis taking over the world was false. created by post WW2 novelists and propagandists.
The fact that the Nazis begged america to join their cause at one point indicated that they at least initially respected american sovreignty.

The japanese also knew they could not invade, pearl harbor was a suicide mission and that was literally as far as they could reach with their planes in those days. An invasion of america was impossible and they knew it.
Theres a famous quote from the japanese about how impossible invading america would be, even if they did, citizens armed.
Another example, the japanese experimented with sending balloons to america because they could not send planes.

(ﾟー｀)