A large theater chain that has a few around where I live cancelled it on all 247 screens nationwide. I wouldn't be surprised if most of the rest follow. The vast majority of Americans are scared sheep[*]. If this happened in a country where people were brave they'd defy the "terrorists" by going out to see the movie just to show them they weren't scared. Maybe this movie needs to be released in Israel or Iraq or somewhere where people are used to terrorism on a daily basis and don't let it rule their lives.
I don't normally see movies in the theater any more, since the experience gets more annoying every year, but I was thinking I'd go with my girlfriend to see this over the holidays when I heard that ridiculous threat. But now there 1) probably won't be anywhere we can see it and 2) all the publicity about theaters stopping the showings would make her mom crazy with worry (we'll be at her parents) if she finds out.
[*] Just so you know before you flame me, I'm an American, not a foreigner and I don't hate my country. But the response to 9/11 showed quite well what cowards we collectively are. OK, I've said my piece, flame away!