Sure a bunch go to germany and yes germany develops players well most coming from that league can't really translate that into national team success. A big reason is that the national team never really played the style that Germany has played since 2005. Hell, Germany is having trouble playing German football these days.
MLS is also fine until you are say 23. American players have traditionally been late bloomers (and also have stuck around well into their 30s).The competetion is pretty good, playoffs mean that you can get days off during the regular season. Also international duty doesn't add matches onto your body. So you aren't going to be a broken mess by the time you hit 29.
Dunno for over a decade now there's been this desire from the people who run the national team all the way down to the fans to clone the style of football that another very successful national team/league plays. And if this is what everyone wants, that's fine. After all Spain didn't invent tiki-taka. But its not Germany you have to look to, its Italy. When we've been our best we've always played a passable imitation of Italian football (strong on free kicks, direct, effective counters, and even if we aren't defensively sound we usually had a good keeper and kept our shape). Also if you ever watched us play Italy, we've given them fits even when we lost. Only problem is that there is (to my knowledge) no US players in Italy (we'll there was Rossi). Unfortunately, no one is really good enough (pulisic excepted) to start for the handful of teams who could pay them.
You want to make the national team better, go break the bank for Conte. Sure he isn't going to work miracles (w/ a ton of luck a QT finish if they get a favorable group of 16 matchup) but by the time he leaves after the 2022 WC we will have at least an idenity the US can work with for the future, and they'll work their behind off every minute of every match. He's also a good enough manager to find out what our limited talent players can do well and put them in a position to succeed.