When I was a graduate student at Syracuse University, a chorister at St. Paul's Cathedral described a Memorial Day service at which a military color guard trooped down the central aisle at the opening procession, dipping its service flags at the altar.
Memorial Day, that year, happened on the commemoration of the Feast of Pentecost, which celebrates the universal presence of the Holy Spirit in the world, regardless of national or cultural identities. It was outrageous. I wrote a sharp little note to the dean of the cathedral, suggesting that attempting to portray the Episcopal Church as a national church was misguided. I received a mealy-mouthed response from one of the canons. (When they tell you your letter was "well-written," it means they have ignored the contents. See Joyce's "Ivy Day in the Committee Room.")
Later, at another parish, I made use of an occasion to remove items on display in advance of Holy Thursday to spirit the U.S. flag out of the chancel to conceal it in an obscure corner of the undercroft, hoping it would not be discovered.
I am a native-born American citizen who has paid taxes without complaint for more than half a century and has voted in every election save one (a primary election when I had to be out of town) since coming of age, and I will happily dispute anyone who disputes my patriotism.
But I do not believe that the conflation of Americanism with Christianity is healthy either for the United States or Christianity. We live in what the Founders rightly established as a secular republic (though many of them did give lip service to a Deist deity).
So mark the Fourth, and mark our hesitant efforts to live up to its ideals, but pray leave the Almighty out of it.