The Establishment Clause is one comma away from the Free Exercise Clause.
Actually not. It's in a letter from Jefferson to the Danbury Baptists.
Establishment clause deals with the prevention of the Government from establishing one lone religion for the country and outlawing the others.
Biden couldn't come out tomorrow and declare that the "Church of The Silly Walks" is the only recognized and official religion of the United States because it violates the establishment clause.
The reality is there is no constitutional "wall of separation."