What is freedom of religion? It is not actually or directly freedom to think or not think religious stuff, not to the extent that one can, or chooses to, keep one’s thoughts secret. Rather, it is the right to display or to refuse to display religiosity.
If you have freedom of religion, as I think everyone should, and if we all have the right to our own lives and well-being, as I think we should, then as long as you’re not hurting anyone else, you have the right to hold various things sacred: books, statues, symbols, buildings, trees, whatever. And everyone else has the right not to hold those things sacred.
In Saudi Arabia, if you do not act as if you hold certain objects and words and behaviors sacred, your life is in jeopardy.
In the United States, what puts you at the greatest risk of unpleasant repercussions is not the practicing of any particular religion, with the possible exception of Islam or anything that people might mistake for Islam. What the most factors conspire to compel you to in the United States is this: flag worship.