Canada I assume would be a popular selection, perhaps Australia? Lichtenstein? Japan? you choose, one other nation.
Italy, France, Australia, New Zealand, South Korea, Brazil... so many countries I've been that I can see myself living in for long stretches.
New Zealand, South America, and Africa will be farthest from the nuclear clouds after the war later this century. I'd move my descendants now to New Zealand, so the family name and genes survive.
I could (but haven't) apply for Canadian as my mother is Canadian. Came very close to doing it and moving to inner BC but chose Beautiful Central Oregon instead. It's still a possibility if America doesn't make healthcare affordable soon.