How Can Islam Be Legally Constrained in the United States?

I’ve been trying to understand how people might be able successfully to mount legal challenges to some of the mosques in the United States.

It seems the U.S. Constitution prevents us from setting up legal limits on Islam's religious aspect except in those cases where Muslims explicitly support violence.

But I wonder if any legal challenge could be successfully mounted to the political aspects of Islam. The fact that Islam does not separate religion and politics does not mean that we, non-Muslims, cannot legally compel such a separation on Islam in the United States and the West.  Robert Spencer has advocated that.

As individuals, Muslims are apparently within their First Amendment rights to advocate that Islamic law replace the Constitution, provided they do not support violent or forceful replacement, and advocate only democratic means.  Insofar as Islamic law and belief do advocate violent overthrow of the U.S. government, that advocacy seems to be legally defined as the crime of sedition, in theory punishable by ten years in prison. 

Religious organizations are legally permitted to influence politics in the United States, but may not actually seek to run the government, not without losing tax-exempt status and colliding with the First Amendment. To the extent that a mosque supports a particular political candidate, or supports the introduction of government policies that are specifically Islamic (even if there is no advocacy of force or violence), it might be possible to get courts to classify such mosques as political organizations, which are not entitled to tax exempt status. And it might then be possible to mount a First Amendment challenge against the very existence of such theocratically ambitious political organizations.

But I wish experts in constitutional law would help the Islam-critical movement to better understand whatever legal options we might have.