回複：請好心人幫助，關於去加拿大登陸的出入境問題

US costume is set in Vancouver. So, you need to talk to US visa officer before you can get on airplane.

You will not see the Canadian Costumer. Your passport will be stamped by US VO with the entry date.

Flying to seattle is much cheaper than flying to Vancouver directly. Additionally, the flight to Vancouver usually stops at Seattle first. So, it do not save a lot of time.