Why do you expect the DPRK to collapse? It was doing much worse during the flooding in the late 90s and early 2000s, where famine was rampant. Even Forbes describes their current economy as "booming," and that support for the government is higher than ever. If they were going to collapse, it would have been in during the aforementioned Arduous March, not anytime soon.

Where are America's going to go when they collapse?

They have the nukes and missile tech to launch them, but lack early warning systems against imminent attacks.

They have Russian and Chinese protections now, but if they go rogue and try to launch first I have a feeling the entire country is gonna get pre-emptive blasted to bits before the missiles leave the pad.

I'm sure Russians have submarine nukes aimed right at NK too for such scenarios