I do think that most of these are US, though...at least the NES games. The only NES games with -CAN were first party releases and with a black sticker seal as far as I know. Given that the NES games in the auctions are sealed with shrinkwrap, the first party titles are probably the -USA versions.
I'm sure it's a mixed bag, that's why for hardcore collectors these auctions may be a bit misleading. I'm pretty sure I had seen the red Mattel logo on the Mario 3 in one of the first auctions and the Mario Paint was definitely Canadian.
As for the rest, it's hard to say without seeing the back covers in detail. I had thought about bidding on a few but with the uncertainty of their region I wouldn't know for sure what country they are from, and for that price wouldn't take the chance.