I live in a state (Texas) that spends more on abstinence education than any other state yet we have one of the highest teen birth rates in the nation. We still don't realize that not talking about sex doesn't mean that kids won't have sex....it just means that they won't know what they are doing.
We definitely have more teenage mums but there are two reasons why it's not always prudent to compare the U.S. to other Western nations:
1) We receive a large influx of immigrants from Latin America and they have almost single handedly contributed to the population growth the U.S. has had in the last 25 years. Blacks are having a reasonable number of children but enough middle aged and elderly blacks are dying off to keep our numbers consistent. Whites are having even fewer babies.
I don't agree with everything in this article but some numbers are highlighted
http://www2.hernandotoday.com/content/2008/jan/26/ha-anchor-babies-weigh-down-economy/
2) A second thing to consider is that while there are more "wealthy" people in the states...there are also more "poor" people....poor being uneducated, unskilled with little access to health care and preventative care. The disparity between the top and the bottom is much wider and the lack of a prevailing monolithic culture means there will always be great extremes....some good and some bad.
This is still a Puritan country at heart....we don't have as much of an Enlightenment view of religion as the rest of the West. We aren't exactly a theocracy either but we are only slightly past the midpoint towards religious "liberalism" while other Western nations are more secular.