The thing is that the NFL in Europe could work, but it would take a lot more than just one team to do so for travel considerations alone. If it's just one or two teams over there, the only way it'd work would be for them to do something like a quarter of the season at home, then half the season over in America, then the final quarter of the season back home. There'd be no way for a team to realistically fly across the ocean on a weekly basis and remain competitive, and that's a tough schedule even segmenting the season like I suggested.
They'd instead likely need a division or two's worth of teams in Europe playing and letting them have a good deal of road games on their side of the pond, and I'm doubting that there are 4-8 parties that want to pay billions for American football teams.