CONCACAF get 3 and a half places.
The top two are decent sides.
But the standard of the teams not the top 2 is so low that they have to really try not to qualify.
I mean in 2010, 3rd and 4th were Honduras (who didn't win a game at the world cup) and Costa Rica (who lost in the play off). In 2006, 3rd was Costa Rica (who didn't win a game at the world cup) and 4th was Trinidad & Tobago (who didn't win a game at the world cup). In 2002 they got three and the third team, Costa Rica, didn't get out of their group. In 1998, the third team, jamaica, didn't get out of their group and in 1994 the thrid team, Canada, didn't get past Australia in the play off.
So ignoring the top two, over the last five world cups that's seven teams. Two fell at the play off. Three out of the five who made it didn't win a game at the world cup. The other two beating only china and japan back when asia were terrible. And none of the seven made it to the knock out stages.
I think USA and Mexico have been, at various stages, good enough to qualify out of UEFA. So they really really have to feck up to not make the top 4 in the group of 6 of crap concacaf sides. Which is why they always do it.
Mexico have been to more world cups than 4 of the 8 nations to have won it. And they've never got further than the QFs. So qualifying can't be all that hard.