There are different practices on which different organized religions depend to keep the "count of the believers" steady and their influence strong which could actually be criminalized when there were enough consciousness and willingness (without disallowing individuals believers to believe). But there surely isn't enough willingness, especially not in the US where publicly "non-believing" more or less excludes you from the politics (shouldn't that be changed for the start?) and the religion organizations have the status of the... sacred cows.

Looking back, there were many very good reasons why the religions were not put in the constitution.