My family owns and operates a few of the ups stores. I rarely work there, but have been to all of the management training crap. Through the UPS, FedEx, or any private shipping firm It's an absolute pain to ship to foreign countries, and canada is one of the worst in north america. Basically the package goes through a brokerage firm that has to be paid on top of the customs fees. Then if the package isn't picked up by the receiver, it gets shipped back to the sender who is charged for the round trip as well as additional processing fees. It's absolutely rediculous.
Since the usps is federal, the canadian government is a little more lax and it's much easier to send; less paperwork, lower tariffs, etc. The main problems is there is a high loss percentage, around 5-10%. Also the usps won't recognize a package as lost till it hasn't been found for a couple of months. But all the same, the USPS is the way to go to canada.
And yea, usually in foreign shipping DEFINITELY mark it as gifts less than $50 (it varies based on country however)
It's literally much easier and possibly cheaper to ship to Europe than Canada.
If you guys are intrested, in domestic shipping the weight split is 3lbs. Over 3lbs UPS is cheaper, under USPS is cheaper. And if you are going ups, pack it yourself. We make more money on packing than shipping.