PEW research center is a nonpartisan, generally trusted source. And the US Census Bureau's numbers are generally accepted as feasible. Even if the US government stopped all immigration tomorrow Americans of European descent would still become a minority by 2050 according to current trends.
The actual numbers could also turn out to be a lot worse. There is currently a positive feedback loop where non-western immigrants overwhelmingly vote for parties that let in more of their own. Mexicans in the US are an imported voting block for the Democracts, as middle-easterners are for Labour in the UK, which means that had Hillary won the Democrats, already holding the majority of the non-white vote, could have tipped the scales in their favour for perpetuity. This is another reason why mixing mass immigration with democracy can be dangerous.
You see the same pattern replicated everywhere in Europe. Turks in Germany generally vote for leftist parties in Germany (69.8 percent for the social democrats, SPD, and 13.4 percent for the Greens) but for hard right, islamist parties at home (overwhelming support for Erdogan, among 1.4 million eligible voters in Germany 63 percent voted pro-Erdogan in the last referendum, that's higher than among Turks actually in Turkey).
In 2015 in the Netherlands two turkish-born members of the Dutch Social Democrats founded an immigrant party called DENK. In 2017 this party won three seats in parliament and won even more votes than the Social Democrats in large cities like Rotterdam and The Hague. DENK has close ties to the AKP and supports Erdogan and Turkish government policies over those of the rest of the Dutch parliament.
It's almost as if these groups vote to help their own in-group (like blacks of whom 95% voted for Obama)..
