I think this has nothing to do with politics. It has to do with the following:
1. Incomplete information on billing, invoices - that will in a certain way force customs to search inside the box when in doubt, and I doubt US customs are more carefull than the canadian ones....
2. Improper packaging - have you ever seen the boxes for - let's say, the Sonus Faber Grand Piano? How flimsy can you get ? It may come from Italy alright and may be ok for smooth-sailing transport on a ship, but forget routes and mileage in the truck from the man in brown.
3. I know of many broken speakers, yet the damages on amplifiers are much less frequent.
4. Many employees from UPS and others just don't care, and this has nothing to do with canadian or american differences.
5. International shipping is always more hassle.
Last time I checked, Audiogon is still taking money from canadians and enjoying the business, so as far as I am concerned, it is north american in coverage and member origin and the site is set up for this. I do not take it too well that people will encourage others not to do business in Canada both ways. Whenever I paid out to a US seller, I was glad I did, and so was the seller as he gladly cashed the money order. It's a two way street, at least for most of us I think. If one cannot face the facts or take the slightest chances or risks, there's always your friendly snobby Hi-Fi shop nearby, with insane profit margins. And that's on both sides of the border too.
The same shipping problems could occur if you shipped something over a great distance within the US.
think about it...