The system is really flawed, but everyone knew that.
Because the US wins were friendlies (I don't know if the Gold cup win counts in the current ranking) they are only weighted 1 time. UEFA qualifiers are weighted 2.5 times. The African and Asian teams are also in some qualifiers or tournament, I think, so they are also have a jacked value.
So a win (3 points) against Germany in a friendly is worth 597 points ((200-1) * 3 * 1), but a UEFA qualifying win against the number 50 team in the world is worth 1125 ((200-50) *3 * 2.5) points. So a win in UEFA qualifying against the number 120 team in the world generates the same number of points as our friendly win against Germany.
They also average all of the wins, so a couple of big wins (Germany + Netherlands) plus a win against crappy Guatemala, actually pulls the average down.
My numbers might not be 100% correct but I think the jist is.
IMO higher CONCACAF teams (USA, Mexico, Costa Rica) are always going to be screwed because they don't have to qualify for the Gold Cup and when we do play tournaments or WC qualifiers they are against lower ranked teams so we never have a chance to jack up our rankings. We pretty much have 1 chance every four years to help ourselves.