a) Canada would probably be involved. Just like it was with 1st gulf war, and Afghanistan, and Kosovo, and pretty much most other things other than the Iraq war. (And while we didn't send troops, there was still all sorts of backchannel support)
b) This ain't the 60s. Unless your kids are Canadian citizens our gov't would just deport them back.
Also it's not like the US has or needs a draft. By the time conscription became such a thing in such a war, the world would be so far f*cked that Canada wouldn't be a place to hide :-(
(Also just because they're Canadian citizens, we have extradition treaties with the US, and if they were breaking a US law, there'd be process. Dodging the draft is a crime. The 1960s Pearson and Trudeau govt's tolerated Vietnam draft dodgers. I'm not convinced a 21st century one would do the same)
War sucks. Let's not have one.
It does have a draft, it’s just not active. You still have to register for selective service as an adult male.Now , I don’t think that it’s ever going to made active again.
As far as needing a draft, there does seem to be a shortage of recruits, notably in the Army and Navy. The army has ads now basically guaranteeing new recruits choice of their duty station, and I’ve seen some interesting signing bonuses from the Navy, but most of those big bonuses are for things like physicians, where you’ll make a ton more money somewhere else anyway and probably aren’t hurting for work.
Honestly though, watching my father try to navigate his mid and late military career, and seeing my brother navigate his early career, I’m not shocked no one wants to join. They seem to be more interested in creating middle managers and bureaucrats than soldiers and fighters. I do have a friend who seems to enjoy it, but mostly because it provided him stability to support his daughter.