Answer: It has.
Morgan Guyton is a Methodist college pastor in New Orleans, Louisiana. He blogs at Mercy Not Sacrifice.
In this piece, Guyton looks at the obsession white evangelicals have with respect for the flag, so much so that it has, for many, become a quintessential part of a Christian value system. He says that this is very nearly the equivalent of offering the obligatory pinch of incense to Caesar, a thing which many early Christians died horrific deaths to be able to refrain from doing. If you are going to argue that an essential part of your Christianity is doing something which the early Christians died for not doing, then your Christianity has become secularized.