Now let's be reasonable. We can't just arbitrarily shut them all down! Due process, and all that.
Make random inspections of every mosque in the U.S. If weapons, explosives, terrorist manuals or hate literature is found, raze the building the following day.
If nothing illegal or incendiary is found, pat them on the butt (but take no pictures!) and go on to the next one...
We need to take a hard serious look on who came up with the money to build each mosque --- it's known that many --- up to 80% or more of the mosques --- were built from Saudi government money. Follow the money --- and any mosque built by a foreign government should be highly suspect.