They weren't charging this before? I must have had things shipped via UPS Ground, then, because I kept getting hit with a $40 brokerage fee (but it's been a couple of years because I stopped using them). FedEx and DHL use a sliding scale based on the value of the goods, and USPS is a flat $5.
Needless to say I've tried to use USPS shipping whenever possible from the US - it's a bit slower, but if I'm not in a hurry then it's a much better value. And, of course, if Canada Post isn't on strike