My religion permits gay marriage. So why can't I marry a woman in the USA?

You know I wrote an entire (long as f*ck) essay on gay marriage. And I spent a lot of time researching. You know what I found out? Gay marriage is actually protected by the Constitution’s commitments to liberty and equality; The US Supreme Court declared in 1974’s Cleveland Board of Education v. LaFleur that the "freedom of personal choice in matters of marriage and family life is one of the liberties protected by the Due Process Clause.”To deny same-sex couples the rights to marry is to also say that it is acceptable to discriminate against them."