Either way it would take years before Hitler could reasonably plan an assault on the US, without the Soviet Union Hitler could not hope to match America's industrial output within 20 years, and even then it would take years to rebuild the damaged factories, and Britain would definetly have started using gas on the Germans when they invaded and the British to would have fought like maniacs, while Britain is a small country they would have fought like hell to defend every inch of it, millions of Germans would probably be wounded in an invasion with the death toll in the Hundreds of Thousands. And Hitler would need to build the Carriers to use in an invasion of the US, along with the transports, battleships and destroyers for coastal bombardment, and a true carrier borne plane would need to be developed. So either way it would be years before Germany could hope to invade the US, something like 1955 at the earliest, and that is assuming that we were not already in a war with Japan, which was doomed to happen after we cut off their oil supplies, we may have been able to defeat them before Germany was able to defeat the UK and then focus it's attention on the US.
No, in my opinion the Germans would get their asses handed to them on a silver platter, and once we defeated the Kriegsmarine it would only be a matter of time before we planned an assault in Europe, starting with Britain, and then France, Britain, and the rest of Europe would truly have to admit that we pulled their asses out of the fire, unlike now where we can speculate that Germany might have been defeated without the US, which is in my opinion BS, the only reason the Soviets won the race to Berlin was because Hitler pulled troops off of the eastern front to face the allies in France, his theory being that it was 2500 miles to Moscow and only 500 miles to Paris, he would last longer by fighting the Allies in France with heavier forces than by fighting the Soviets with a majority of his military.