Pffft!
Whatever he does, he'll call it "a YUUUGE WIN!".
Yeah, but unlike, say, the subtle distinction between legislation and executive orders, his followers are very fond of war, and will be able to tell the difference between wins and losses and mired down in another endless bog... It'll be harder to convince them that Up is Down on that one...
National leaders don't need to WIN wars to become popular. Indeed, history suggests that losing is the better route to popularity for a leader. When your troops are winning great victories, you need to convince the people that they are still at risk, and need your strength to protect them, but when you suffer a major military setback (particularly one that leads to civilian deaths), the people will fall over themselves to support you.
What you need to gain popular support is a credible threat. Iraq, Afghanistan and Vietnam were losing wars (or stalemates) for the US, but more importantly, they didn't project a credible threat to the folks back home. Pearl Harbor and 9/11 were real threats - neither was a victory, but that didn't matter. Churchill was never more popular than when he was standing alone against the might of the Nazi war machine; but once the war was won, the British public voted him out of office.
What Trump (like any weak leader) needs to consolidate his support is not a war
per se; it is a credible and widely accepted threat to the American people. North Korea might fit that bill, but only if the people genuinely believe that Kim can hit the USA with a nuke. Certainly when viewed from the other side, Kim is very successful in persuading his people that Trump and the USA are an existential threat to North Korea - and the NK public will put up with astonishing hardships if those hardships mean being protected from 'US aggression'.
If LA or Seattle were to be wiped off the map by a NK H-Bomb (NK almost certainly doesn't have an H-Bomb, btw; and they probably can't deliver an A-bomb to Tokyo, much less the US west coast) then that would be terrible for the USA, but fantastic for Trump's popularity ratings. Particularly when he responds by turning North Korea into 120,000km
2 of radioactive glass.