I've been following the hockey and basketball playoffs only peripherally, but from what I saw, it was Canadians who booed the US anthem first.
I've always thought that the US and Canada had a pretty friendly relationship (thanks in large part to Canadian full-nude gentlemen's establishments) so I was a bit surprised when I first heard it, but I wasn't ready to drop any Nukes on the Canadian capital of Buenos Aires.
What if it turns out that it was, in fact, Americans who booed the Canadian anthem first? I'd still be surprised, but it's only a sporting event, folks. No need to make an international event over it. How about we give you Toledo, Ohio, and call it even?
Hmmm
(Canada has an army?)