Some people think poor in the US have more children than rich. So that would affect the natural selection you're talking about if true.
Yes, that's true. It has long been known as the "dysgenic effect," more recently as the "Idiocracy effect." It works in the opposite direction of the "Flynn effect," which is the observable upward secular shift in intelligence from one generation to the next along any given ancestral line, for an unknown cause but probably epigenetics, 3 IQ points every decade. The Flynn effect is currently faster, overshadowing the dysgenic effect, but the Flynn effect probably has an upper limit and will eventually stop, and the dysgenic effect has a very distant theoretical lower limit, so the dysgenic effect will probably win in the end.