Quoted from flashinstinct:
Shipping something something to the states from Canada is literally a 60 second affair when you are at the post office. The form we fill is essentially your mailing address, the destination address, box content and price of materials.
Guy punches a few keystrokes, postage gets printed...done deal.
This is true for smaller items, for larger ones it gets more difficult (especially with insurance) as: 1) US customs requires you to ship in a min size box (doesn't matter if it is a spring) - the box/envelope has to be large enough for the customs form to fit (can not bend around the edge), 2) all the info on the customs form has to be typed into the computer a pre-submitted to US customs (no idea why, just what I have been told). An easy 10-15 minutes once you get to the counter (and I always seem to get stuck behind some person that needs to send money via Western Union to some 3rd world and can barely speak English...grrrr).