Muslims have the freedom of religion NOW to practice Islam (or any other religion or none) in any way they want.
The Sharia Law, on the other hand, is just that. It is NOT religion. It is an imposition of rules (law) on how Muslims MUST practice Islam.
What you are demanding is a law to FORCE American Muslims to practice Islam the way YOU want them too. That is not freedom of religion. Nor is it constitutional.