There are two big issues.
The first is the confederational fudge factor, basically FIFA admitting that they suck ad making a rating system and need to put a thumb on the scales to get it to come out "right". The really pernicious part of it is that we get a piece of that fudge factor in every single game we play, even if by some miracle we were to end up in the top five in the country, we'd still get our points downgraded in every game we play because we're from CONCACAF.
The second is that games in official competitions are worth a lot more than friendlies, and there's imbalance all over the world in when official competition games are being played and the quality of teams being played in those games. We could end up in the 20's not because of any fault in our results, but merely because European teams have been playing in the European Championship while we've been playing qualifiers against Antigua and Barbuda.
It's certainly true that we had a tendency toward being overrated under the old FIFA rankings formula, but it's also true that the new one has several built in brokennesses and is basically designed to screw everyone from CONCACAF and AFC.