I think he has improved from a year ago. He has shown an above average ability to defend one v one, and his speed has been enough to cover some of his mistakes. Is he "good?" He is the best option we have at the position but has been the worst of the 4 starting defenders. Besler needed Bedoya to help cover his side. He still makes a lot of mistakes and he isn't going to be playing for a CL team anytime soon, but he has been good enough outside his mental breakdowns, which is the worst part of his game. If Yedlin had game sense of Besler, he'd be playing for a better club.
But if you are asking for the most dissapointing performances from the US squad in this tournament Yedlin is in the top three with Zardes and Bradley. The team hasn't play as well as it has in the last three games since 2009/10.