Islam is not compatible with the US Constitution. They should be made to swear allegiance to the Constitution over Islam or be denied entry and citizenship, which could be revoked if proven that their oath was a lie.
Even if they were to forswear Islam, the principle of taqqiya condones (at best, demands at worst) lying to the infidel. Any oath of allegiance to anything other than Islam is void to them.
Not to mention that leaving Islam marks them as apostates, subject to a death penalty.