Couple of things......
1. US was not defeated in the war of 1812. Washington burned. But the war was won by the US.
2. An untrained and outnumbered militia that had very little domestic support defeated the British the first time around.
3. There were plenty of VC running around after Tet.
4. While not the mainland...read here.....
Aleutian Islands Campaign - Wikipedia, the free encyclopedia and here for some Japanese thoughts......
Isoroku Yamamoto - Wikiquote
5. No resistance? 320 million people approx in the US. Approx 80 million gun owners. Lets say 90% of them don't resist and or turn in what they have. That leaves 8 million gun owners that are hard core and determined. Sorry.....you can bet there is going to be domestic resistance.