Have you even seen the original? They dont take the whole US. Its a temporary invasion of one coast.
Of course I have
I'm an eighties child
But then, that was the original, which didn't involve some EMP attack. IIRC, when the Soviets were the villains, they managed to nuke several key targets (apparently without warning, which is b.s., but hey: it's a classic and I'm willing to suspend some disbelief for John Milius' sake alone
) and split the country in two -- along, of course, with the help of some sneaky Cuban and Nicaraguan invasion forces moving up through Mexico.
Regardless, my point stands: whether or not the entire continental U.S. was nullified by an EMP weapon the N. Koreans don't have, U.S. submarines would make any encroachment on our soil completely bittersweet -- not even a pyrrhic victory.
I mean, shit, the sub fleet alone's got, what, maybe a couple of gigatons worth of nukes? North Korea is small. Several dozen properly targeted kiloton-ranged devices would ravage their homeland beyond hope. And it's my understanding that any large invasion force on U.S. soil is open season for nuking. Part of that depends on the invader's proximity to very large population centers. But a town of 100,000 Americans or less occupied by a key enemy base? The "word," at least as I have it, is 500 kilotons, minimum.