As we're waiting the first results of 2020 Census:
U.S. Population Growth In 2019 Is Slowest In A Century
I don't think the US will ever again see natural growth above 1 million/year. In
2018 it droped below 1 million for the first time since 1937 (when the country had only 128 million inh.) and in 2019 another drop, to
890k. Needless to say 2020 will be a disaster. 1Q/2020 numbers are already available dropping to 113k compared to 149k in the previous year.
From now on, the US will become Europe: population growth will depend almost exclusively from immigration.