Eventually, for everyone. Teen births are already on decline (thank God) and Mexico already has a lower birthrate than America. Birthrates have dropped in places you wouldn't believe. 2100, the population will be the same as it is today according to UN. Historically, immigrants have more kids than Americans, that's always been true. But family size shrinks. Once, we face the same issue as Japan it'll get ugly. Picture towns and smaller/weaker cities across the country becoming mini-Detroits or ghost towns. The place to be in the future will be the big city or close to it b/c that's where the intellectual/$$$$ capital will be. Any hope of a legit job will be in the city.
I don't fear it but society will need to form new paradigms in order to cope.