Upvote:1
Most airports have a single check in counter, but some larger hubs may have separate counters for domestic and international check in.
As your final destination is outside the USA you would check in as an international passenger. They will usually check your passport when you check in and drop your bags unless you check in online and don't check any bags. If you do the online check in, then the gate agent for the international flight will ask to verify your passport.
Upvote:2
Everyone will be called to the gate agent for passport check before boarding the Canadian plane. It can't really be done before; there are no airports with dedicated transit areas in the USA.
Upvote:3
I have never seen separate "domestic" and "international" check-in areas or procedures, including in situations similar to OP where I took a domestic US flight followed by an international one out of the US. Everybody checks in for the first flight in the same way, regardless of any subsequent connecting flights they may or may not have.