Is TSA in foreign airports for US bound flights? I was surprised last year when coming back from France through Canada, that I went through US Customs in Toronto.
The CBP screening, that's a pre-clearance thing, where we have officers in foreign ports to screen passengers before they arrive here. It's kind of a convinience thing, I guess. Get you processed before you're tired from an international flight. It's the same thing you go through when you arrive at an airport here.
Do you remember if the CBP guys on duty in Canada were screening for weapons, or just things like (CITES, Fruit, Meat) a rhino horn full of heroin and Khapra Beetles?