Except for one thing: immigrants (legal or undocumented), who normally have more kids.
That's the difference between America and most other first-world democracies - as idiotic and as racist and as backward as our society often is, we're still more open to immigrants than most other nations.
Your article would have been more accurate had it emphasized white Americans' demographic future. That's important, because the browning of America is actually one of the main factors that will preserve our economy and our society, no matter how much the white Right will try to deny it.