The US has a fertility rate of 1.6 (https://apnews.com/article/fertility-rate-us-low-cdc-replace...), i.e., 1.6 kids per 2 parents. Better social services and social safety nets would likely increase this some, but it would still probably be under 2, since that's the general trend for wealthy countries.
Opposite actually. Prosperity and security decrease fertility. Go look at the most developed nations is Europe and Asia and they have lower fertility than the US. America is only hanging on due to latent religious fervor (and immigration).
Interesting way to sidestep the answer, because I did not ask you what the current rate is. I asked you why you think the existing population cannot breed.
If it is social services and social safety net, then why the same does not apply to the immigrant population ( legal or illegal )? Again, I know what I am thinking, but you have to give me a little more so that I model your world perspective a little more clearly.