[thoughtomator]

Hawaii, Alaska, Vancouver, Guam, the Philipines, or Australia?

You're making unproven assumptions
(1) The NKs can reliably have any their missiles hit targets at range
(2) The NKs can plausibly have all their missiles hit the indicated targets
(3) The US is not able to mount any defense to these missiles
(4) China would militarily intervene in a NK-US conflict against the US

You've also made an unproven assertion that NK has missiles that can reach the indicated cities.

In addition, I do not believe the Chinese would realistically attempt to seize the Panama canal. It is far too difficult for them to hold and too easy for us to remove them. A serious US-China conflict would resolve itself by nuclear strikes, so there would be no point for the Chinese to do that. There are also allied forces in Japan, South Korea, Australia, the Phillipines, and Taiwan to be factored into the equation.

Direct US-China military conflict is unlikely in the extreme (not that we shouldn't be prepared for it if necessary). We have too many advantages, and would never be the ones to initiate it. The Chinese are not insane like Islamofascists and the NK regime.

I find it more likely that in the event of US-NK conflict, the Chinese will attempt to take over NK to block an expansion of US influence.

[The Pheonix]

I agree with both your postings

[Lunatic Fringe]

I do not believe the Chinese would realistically attempt to seize the Panama canal.

They already control the canal... Clinton handed it over in 1999.