So, first, you claim there are several problems but then attempt to disprove only one.
Second your "proof" is nothing of the sort. Other countries won't take Canadian dollars for their goods? Prove it. Corollary: Also prove there are no such things as currency exchanges. Oh and by you logic other countries wouldn't accept US dollars for their goods - and we know that isn't true don't we.
But hey let's say for the sake of argument that they do spend their money in Canada. So, great, we get a lot of trinkets and then they end up owning more and more of Canada. 
If you want to jump ahead to the punchline just go ask natives how that worked out for them in the US and Canada.