We'll just let in an equal number of Mexicans..
But seriously, the Muslim population in the US is about 1%, and people are losing their minds over Muslim immigration in the tens of thousands per year - ridiculous.
And, even if Muslim immigration did outpace assimilation, it's not the apocalypse. Contrary to the hysterical propaganda, we're not going to wake up one day beheaded and crucified. Worst case scenario, you get the kind of ethnic tensions that existed around the turn of the century (rising to the level of minor nuisance in the grand scheme of things) and a turn toward social conservatism (which most of the anti-immigrant folks favor anyway, oddly enough).
Now, Europe is in a different and more dangerous situation (not apocalypse either, but more terrorism), since they already have fairly large Muslim populations who failed to assimilate because of the welfare ghetto strategy the idiot (non-Muslim) leadership pursued. Don't repeat their mistakes, and we'll be fine.