The new rankings were tough for all of CONCACAF. In addition to the U.S. and Mexico both falling, Costa Rica, Jamaica and Trinidad and Tobago all well downward. That's not entirely surprising because their September World Cup qualifiers from 2013 and 2012 were weighted less heavily and for a confederation that doesn't play a ton of tough matches, especially tough competitive matches, losing qualifiers will hurt. The U.S. losing to Brazil last month didn't do them any favors either.
Argentina are still the top ranked team in the world, followed by Germany, Belgium, Portugal and Colombia. Spain made a big five-spot jump to No. 6, rejoining the top 10, with Brazil, Wales, Chile and England trailing them.
In the case of the U.S., the FIFA rankings don't mean a thing. They will always be high enough to be seeded for CONCACAF events and were never going to jump high enough to be seeded at the 2018 World Cup draw. Those are the only things the FIFA rankings really affect so no harm done, even dropping a spot.