I have bought thousands of items from the U.S. over the last few decades, and USPS has NEVER failed to deliver to me here in Kanada. And no extra fees upon arrival either.
UPS is the absolute WORST delivery method to Kanada. If you are lucky enough to receive your package (don't count on it), they will hold your pkg ransom until you pay at least double in fees once it arrives here. And if (when) they "lose" your package, don't count on their insurance to cover you - it less than worthless (you paid for nothing).