When I watch European soccer I don't usually root for anyone. I have no favorite team, so I just watch with little emotional involvement (nothing like watching a Met game, believe me).
Now, however, there's one team to root against Inter Milan. Inter has opted to stay home rather than play a pre-season tournament in England. I don't know if it's possible, but I'd be big fan of any team that stepped into the breach here.
I'd love to imagine that the MLS will nominate a team to come to England for the 4 dates. Or send an All Star team or the US National team. {And, I know for the soccer fans in those 4 cities this would be a poor substitute, but it would at least show the Italian club to be the wimps they are.}
UPDATE: Okay, I'll take back my vow to root against Inter Milan wherever they're playing. They feared my wrath, I know, because they've decided to go ahead with the tour after all.