I am guessing the bump from late 1980s to 2000s was almost entirely due to immigrants, especially Latin American. Similar to a bump seen in other countries where immigrants coming from places with higher TFRs bumped it up, and within a couple decades, even those immigrant populations now have lower TFRs.
https://fred.stlouisfed.org/series/SPDYNTFRTINUSA
I am guessing the bump from late 1980s to 2000s was almost entirely due to immigrants, especially Latin American. Similar to a bump seen in other countries where immigrants coming from places with higher TFRs bumped it up, and within a couple decades, even those immigrant populations now have lower TFRs.
https://ourworldindata.org/grapher/children-per-woman-un?tab...