The problem is the US doesn't have the infastructure to train and develop players like most all other countries in the world do. The investment required just isn't there currently. This was one of the main things Klinnsman wanted to change when he came on board. The MLS is modeled after American sports, with the draft, playoffs, etc., to keep interest in the American sporting public who just by and large doesn't understand promotion and relegation and I'm not sure MLS is a deep enough league to be ran in that fashion anyway.
MLS teams need to establish their own acadamies to develop young talent. Letting kids go through the current system and relying on colleges to develop them further will never achieve the results that people want. I know some MLS teams are doing this, but it needs to be a point of focus for the league to develop players for the national team, not colleges and youth club traveling teams.
About Shea...well I've never really been impressed by him. But I love seeing Americans pack up and head over to Europe. Anytime a young player can get some time in Europe is a great thing and to me is by far the best thing they can do to advance their game mentally and technically. Getting the experience of playing in the EPL and training with an EPL team will grow him quite a bit.