As a fellow American (and Godless Sodomite), I wish to inform you that I support your First Amendment rights to free speech. Freedom of speech is critical to the health of our nation, and even the most unpopular speech needs equal protection under the law. No matter how much I may disagree with you and the hubris that is displayed on your billboard, we are both American citizens regardless of our personal views on such things. There is room for us all, we don't have to be neighbors and we need not even like each other. How you live is none of my business, and frankly, unless you're impugning my civil rights, you don't matter to me at all, you have no affect on my life, and we will likely never meet - but I still support your rights as an American citizen to say whatever fishbrained, psychoreligious babble you wish to profess to the amusement of logicians everywhere.
I would also like to remind you that the United States of America is not, contrary to your view, a Christian nation and Jesus was not an American citizen.