The former Manchester United player’s contract expired at the end of last season after 5 years at the club and the Hammers did not offer him a new contract.
Birmingham manager Chris Hughton told their official website, “"Jonathan is a player who has got experience of playing in the Premier League and as an international for America so he has good credential and at 25 he's at a very good age,”
"He is versatile and can play in a few positions. I think he will be a big asset for this club."