Kim Jong Un would, and China's a big ally to North Korea alongside Russia.
Interestingly there's an increasing rift between China and NK. The constant crazy things they do, (as well as occasional attacks on Chinese citizens) have lead to the populace and government hating the country. It will be very interesting to see in 2021 if they renew the Mutual Defence Treaty, because as of right now, there's a likelyhood that it won't be. Which in turn, would allow another country to invade NK without Chinese intervention.
Who says China's NOT making rail guns to fire at us?
No one, as they've publicly confirmed and bragged about having the worlds first ship mounted Railgun (albeit a test unit). It will probably take a few years before they're ready to destroy aircraft carriers though, RG's take immense amounts of electricity, and require heavy maintenance.
As i've said before though, they're not going to wage war on Canada. Their attention is with other countries who they actually have issues with.