I'm not sure. In real terms it would make little difference to me, Manchester to LA is probably easier than Manchester to St Louis.
But I love St Louis sport, be it Rams, Cardinals or Blues, I'll even support the Billikens as long as they aren't playing my Gators.
I'm also not sure I can support an owner who rips the heart out of a city for simple financial gain, it's just such a foreign concept as an Englishman (look to Wimbledon FC, move 50 miles up the road to Milton Keynes and automatically become the most hated football club in England)
But then again I love the team, I've suffered with the team and celebrated with the team, it would be tough to walk away from a 10+ year relationship.
So to sum up, no idea.