1. - As noted, Euro leagues pay for soccer as well as americans pay for NBA, MLB and NFL and the endorsement opportunities are there. My understanding is that they get a piece of transfer fees as well, which can be ridiculously high (Robbie Keane just transferred to Liverpool for something like $46m).
2. - They would want to be famous in Spain (or Italy or England or Germany) for the same reason Pau Gasol, Yao Ming, Dirk Nowitzki and Manu Ginobili want to be famous in the US. Because that is where the best in the world play and where they are known. Open your closed little minds, there is much east of the Atlantic and west of the Pacific. Europe is a pretty amazing place.
Don't judge American soccer as a whole based on 5 bad minutes of a U23 tournament, which is really all it was (the last minute of NED and the first 3 of Nigeria). While NED didn't have their best players, many of the best Americans were also absent. American soccer isn't comparable to American basketball or Spanish soccer, but it is anything but a disgrace. As long as it is essentially a suburban white kid sport it isn't going to rival either of those two but it is a mischaracterization to call it a disgrace.