Any invader of the United States isn’t facing just the U.S. military, they’re facing all 330 million Americans. and yadda yadda yadda etc...
One thing you're forgetting there Chief, Americans are soft and weak. The country has never been invaded by a foreign nation for the current populations lifetime. The people are addicted to junk food, obesity and diabetes is rampant, no one is 100% healthy and if you manage to destroy supply lines a lot of the flyover states are going to implode. The only real threats are the hill and mountain folk that are lodged up in valleys and hollers so deep a battalion would get slaughtered trying to get them. So ignore them because Americans are dumb as fvck and their government are making them dumber by the year. Go in with shock and awe and 99% of Dumbfvckistanis will fold like cheap suits, the strength of the Greatest Generation (the men who fought in WWII) is gone from the people, they've been pre-demoralized, they hate their country they hate their fellow citizens, they hate themselves. Now or very soon is the best time to invade and annihilate them.