According to this article. It's certainly an intriguing idea, him joining the USMNT, but my understanding is that it takes 5 years from Green card to citizen. I honestly can't imagine that Zak would want to wait that long, especially if you consider that would make his first World Cup hopes 2018. I still think it would be great to see him out there but between the wait and the US being overflowing with good midfielders it seems like it wouldn't really be the best choice for him. Then again, he could turn into something really great in a few years. Who knows?