My suggestion is to recognize Atheism (or the lack of a belief in a god) as a religion in the United States.
There is no actual scientific proof that a supreme being does not exist, thus to say there is no God is to express faith or belief in the idea that there is no God and to force things like prayer out of the public square is forcing one persons beliefs onto another thus trampling upon their rights.
The first amendment grants both the right of free speech and the free practice of religion.
Implied in that idea is the idea that we need to be tolerant of others beliefs. Currently the major push is for the religion of Atheism to stamp out the rights of others, however we would not want their rights to be trampled on either so put both groups on the same level as they should be.