Of the arguments against allowing muslims to build an Islamic community center (not a mosque for Pete's sake) in lower Manhattan (not at ground zero), Ross Douthat's has to be the silliest. 

As is often the case, it starts out sensible:

There’s an America where it doesn’t matter what language you speak, what god you worship, or how deep your New World roots run. An America where allegiance to the Constitution trumps ethnic differences, language barriers and religious divides. An America where the newest arrival to our shores is no less American than the ever-so-great granddaughter of the Pilgrims.

Hurray for that America I say.  But there's another America:

But there’s another America as well, one that understands itself as a distinctive culture, rather than just a set of political propositions. This America speaks English, not Spanish or Chinese or Arabic. It looks back to a particular religious heritage: Protestantism originally, and then a Judeo-Christian consensus that accommodated Jews and Catholics as well. It draws its social norms from the mores of the Anglo-Saxon diaspora — and it expects new arrivals to assimilate themselves to these norms, and quickly.

Not so good.  I don't like that America so much.  What will Douthat say?

These two understandings of America, one constitutional and one cultural, have been in tension throughout our history. And they’re in tension again this summer, in the controversy over the Islamic mosque and cultural center scheduled to go up two blocks from ground zero.

I'll even grant the dichotomy–for the sake of characterizing the general dialectical terrain–even though it's egregiously wrong (not "false" however in the fallacious sense).

The first America, not surprisingly, views the project as the consummate expression of our nation’s high ideals. “This is America,” President Obama intoned last week, “and our commitment to religious freedom must be unshakeable.” The construction of the mosque, Mayor Michael Bloomberg told New Yorkers, is as important a test of the principle of religious freedom “as we may see in our lifetimes.”

The second America begs to differ. It sees the project as an affront to the memory of 9/11, and a sign of disrespect for the values of a country where Islam has only recently become part of the public consciousness. And beneath these concerns lurks the darker suspicion that Islam in any form may be incompatible with the American way of life.

This is typical of how these debates usually play out. The first America tends to make the finer-sounding speeches, and the second America often strikes cruder, more xenophobic notes. The first America welcomed the poor, the tired, the huddled masses; the second America demanded that they change their names and drop their native languages, and often threw up hurdles to stop them coming altogether. The first America celebrated religious liberty; the second America persecuted Mormons and discriminated against Catholics.

But both understandings of this country have real wisdom to offer, and both have been necessary to the American experiment’s success. During the great waves of 19th-century immigration, the insistence that new arrivals adapt to Anglo-Saxon culture — and the threat of discrimination if they didn’t — was crucial to their swift assimilation. The post-1920s immigration restrictions were draconian in many ways, but they created time for persistent ethnic divisions to melt into a general unhyphenated Americanism.  

It seems there are three Americas then.  The third is the result of the historical-dialectical play between the first two.  But that's not really the point (and Douthat doesn't seem aware of this).  His point is that hegemonic cultural and religous bigotry is morally justified because it forces people to assimilate culturally and religiously.  This way, I think, they don't become victims of racism and bigotry–that would be unamerican.