Ukraine and Georgia probably would disagree with that assessment.

Where does this even come from?

The furthest Germany went in this regard was their U-boats sinking American tankers and merchant ships along the East Coast after Germany declared war on the U.S. in December, 1941. The film, "Das Boat" gives a good feel for what this was like from the German point of view. But it is a far cry from being invaded or any invasion threat. Germany didn't invade England, which was a lot closer, despite having plans to in Operation Sea-Lion. This proves they were not capable of invading the U.S.

"Operation Sea Lion, also written as Operation Sealion (German: Unternehmen Seelöwe), was Nazi Germany's code name for the plan for an invasion of the United Kingdom during the Battle of Britain in the Second World War. Following the Fall of France, Adolf Hitler, the German Führer and Supreme Commander of the Armed Forces, hoped the British government would seek a peace agreement and he reluctantly considered invasion only as a last resort if all other options failed. As a precondition, he specified the achievement of both air and naval superiority over the English Channel and the proposed landing sites, but the German forces did not achieve either at any point during the war, and both the German High Command and Hitler himself had serious doubts about the prospects for success. A large number of barges were gathered together on the Channel coast, but, with air losses increasing, Hitler postponed Sea Lion indefinitely on 17 September 1940 and it was never put into action."