Freedom of religion is the concept that all people person has the right to decide for themselves what they wish to believe. Separation of church and state is the concept that no religious belief shall have predominance in the determination of laws or how this country is governed.
What is freedom from religion? Religion is belief in concepts that cannot be proven as true or false. The study of nature and the universe points to a single system that everything fits into. This is proof of some central organizing force that is a God entity. It is quite likely that God is not a long white-haired invisible magic man in the sky, but that does not exclude the possibility of God as another type of entity.
The idea that there is no God entity at all is as unproven as any other concept and is therefore also a religious belief. Atheism is as much a religion as Christianity, Judaism, Islam, Hindu, etc. Sorry, atheists, but you are also a religion.
All people are guided through life by beliefs and attitudes that contain many things that are without proof. Every thought and breath has effect on what a person is and becomes. These make up the individual religion of each person, which may or may not conform to an established institutional religion. Even the worst criminal still functions by a personal religion that is a bad religion, but it is a religion nonetheless. Apologies to John Lennon, but to "imagine there were no religions" is to imagine everyone as brain-dead. Even he preached a religious belief. There is no such thing as "freedom from religion".