Well..every country is different but in my experience it's super easy to get a work visa in most European countries if you're in any technical field. In general I would figure out maybe which country you want to move to first and then start looking into companies, but that's assuming you are ok to leave your current company. This is the one situation where I heavily relied on third party recruiters as they knew obviously know the scene better than I do and then on subsequent jobs I figured out on my own once I got the lay of the land.

The tech hiring market is strong but if you can self employ and are a US citizen the Dutch American Friendship Treaty is interesting.