[I]f the US turns Republican, it'll only be good for Canada and Europe.
If it's happening in parts of the states, it's not in others, and the parts of the states it is happening in, are the places you'd never want to live in anyway, rural areas where the population is bleeding out, atracted to the bright lights, freedom and decadence of the big city.
Absent the US going theocratic loony, there is no downside to firstworlders whether the US returns to sanity, or keeps going to Republica. If it keeps going further to the right, it will export many, many productive college graduates, educated folk, more arts than sciences, but plenty of those too. If it pulls out of the world system into isolationism after Iraq, it's all to the good too. Absent actual psychosis, the US is not life threatening to first world countries, and if it goes right, we will have extra catch up time, and the benefits of the good ones their education system produces, while if it returns to the One True way, we can say welcome back.