These are not silly questions at all, by the way (you apologized above). You are being prepared. If you're going to be in the US for two years, it IS possible you will have a major vet incident. I think you're being smart. A cancer surgery and chemo in Canada can run $10,000-$25,000 or so. It would probably be a little cheaper in the US, but that gives you an idea. If your French insurance would work, that would probably be best to maintain. But if it wouldn't, it might be wise to get a policy for the time in the US.