"Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances."

I am not a constitutional scholar, nor am I even American, but that doesn't say to me that religions can't be taxed, so long as it's applied equally across all religious organisations. If they are taxed like businesses, they are still allowed to be practised, surely? And there is no 'establishment' of an official church or religion by taxing all equally.