Agreed, Curry. And thats assuming anyone is stupid enough to actually attempt an invasion of the USA without most of Europe, or Russia and China on their side.
Like Russia, and china to a slightly lesser extent, the USA is large enough that a ground war would come down to the destruction of military forces, not the capture of territory. Production is too widely dispersed to make viable targets for an offensive, and worst case scenario, we can strip everything else bare, and concentrate AA defenses around the most important targets.
And in addition to that, we have some formidable natural barriers, particularly in the west. I live in the cascade mountain range, and I wouldn't care to try pushing armor through some of these hills. And logistics..... *shudder*.
