If you're a US citizen or permanent resident, you'll be subject to a "self-quarantine" of up to 14 days on your return. As I read the announcement, if you're an alien with say a work or student visa, not a permanent resident, you won't be permitted back in the U.S. until 14 days have elapsed since you were in Mainland China. No exception for Canadians, either.

The other issue is whether or not those flights will be operating in two or three weeks, Look how quickly this is all moving.