I will say, if the accident was a couple years ago, it would seem unlikely that it would impact your ability to use it for a road trip. Really, roadtrip miles are easier than stop and go city traffic. Obviously, a mechanic will be able to tell you what is really going on and if there are any issues that would be a problem on a long trip.
I will also say that if money is a factor, it could be cheaper for you to wait to purchase your car until after you arrive, so you wouldn't have to deal with the potential issues of licensing, titling, etc in 2 states. Seattle's climate could also be easier on cars than what you might be able to buy in Boston.
But having said that, new cars are fun and exciting, and a roadtrip isn't a bad reason to be looking. I'd recommend looking at lot of different models in the crossover segment. Really, the only way you'll know what you like is to get behind the wheel yourself.