It seems bizarre that the Americans would move up despite failing to win a match, but the rankings value who you play and especially what confederation they come from, so playing two good UEFA teams away provided a boost. It also helped that Ecuador, Tunisia, Bosnia and Herzegovina and Ukraine all fell.
But all of that can change this summer at the Gold Cup. The rankings put extra weight on competitive matches and especially confederation championships so Gold Cup matches are going to mean a lot. Whoever wins the competition will get a nice boost, while an early exit could doom a team.
Of course, the FIFA World Rankings don't mean much. The U.S., Mexico and Costa Rica won't be caught by anyone else in CONCACAF so they'll continue to receive byes in qualifying, as they always have, while none are going to crack the top 7 and be seeded at the World Cup. It's more about pride.
Germany are still top of the rankings, followed by Argentina, Belgium, Colombia and Brazil. The Netherlands, Portugal, Uruguay, Switzerland, and Spain round out the top 10.