Why are the American goalkeepers so much better than Mexicos?

I remember when "ochoa" was your savior "one of the best in the world" according to people on here. What a joke the only World Cl keepers in CONCACAF right now are Brad Friedel and Tim Howard, both recently ranked as top 4 in the EPL and top 10 in the world, no Mexican keeper was even ranked in the top 20.