There's no indication that the U.S. and Canada wouldn't co-operate together, especially in a search and rescue scenario because, first, that's the law, and second, there's also the search and rescue agreement, which the U.S. and Russia were instrumental in drafting. In a search and rescue scenario, I can't imagine any country saying, no, we're not going to help. That's just anathema to me.
On October 24th, 2018. See this statement in context.