I believe you are correct in thinking that the US will try to disrupt North Korea from within using the aid of Japan. However make no mistake, China is backing North Korea and will not accept this. North Korea is a buffer state to China (against Japan, South Korea, and the US), as the Ukraine and other Eastern European nations are to Russia (against NATO and the US).

Is it a coincidence then that US forces are the most concentrated in Eastern Europe, Middle East, and Japan? I think not. Both sides are looking to buffer themselves from one another.

This is simply the Korean War continued, which is the culmination of the Reagan Doctrine (anti-communism) combined with the Wolfowitz Doctrine (US dominance). It is the US, Japan, and South Korea (with NATO in reserve) versus China, North Korea, and of course Russia. So when Trump makes bold claims against North Korea, I suspect he is really communicating to China and Russia that the US military will not stand down to any aggression.

Trump is also likely leveraging military force to communicate to Russia and China that for the time being, the US Petrodollar remains dominant and refuses to step down quietly to any alternative coming out of the East.

That's my belief, we will see how things develop! I highly recommend everyone seeing this read up on the Korean War, or "The Forgotten War" that is never taught in schools. I wonder why it's not covered....

https://en.wikipedia.org/wiki/Korean_War