The reason we're not producing many great outfield players yet is because most of our players go play for a university and waste their best development years (18 to 23) getting crap instruction, rather than getting the training they need in a professional club system, preferably a foreign one.
Things are changing though, there are two young Americans in the Arsenal reserve squad (Karbassiyoon and Simek) and I know Manchester United's youth teams are chock full of Yankees. English clubs are starting to realize we have a lot of untapped talent here and they're getting our best young players before their development is put off track during their university years. My generation (I'm 18) is really the one that is starting to go abroad for better training, two guys from my U18 club side are now playing in the regional leagues in Germany (the third division, I think), one is with Atletico Madrid's B team, one at Atlas in Mexico, and a few of us earned trials with Defensor in Uruguay. A few of us may end up earning a living in the game and there were a dozen or so better teams than us in the country, that's how good the young players are here.
Latin countries are scouting heavily in California, Arizona, and Texas, where a high % of the best players speak Spanish and play a very Latin style. In the future, with immigration continuing like it is, you could realistically be seeing many USA internationals playing in Spain and the national team showing a heavy Latin influence.
If you still don't think the USA has any good outfield prospects, I have just one name for you, the future of American (and world?) soccer: Freddy Adu. There isn't one player under the age of 18 the biggest clubs in Europe want more. If he's not considered among the best in the world in 5 years I will be shocked.