Stetzer's definition of church: "The church is the sign and instrument of God's kingdom." While there are many, I'll begin with this.
How much of our culture controls our worship? Granted, we speak the lingua franca of the culture in order to be understood. We dress according to biblical morality yet within societal comforts and recognition. We interact within American cultural norms.
Yet as a church which seeks to reflect, worship & glorify Jesus Christ, how much do we allow our culture to control our worship services? We understand very clearly songs like, "Santa Clause Is Coming to Town" & "Hopping Down the Bunny Trail" are inappropriate for Christmas and Easter worship. Most (though not all) churches have removed Santa Clause from their Christmas worship--especially since 1) he is not biblical and, 2) the Protestant Reformation should have purged Roman Catholic influences from our worship.
So what about patriotic celebrations? Nationalism is a foreign concept biblically. It is laughable to think the early church--especially in the first & second century--would have had a Roman flag or sang patriotic songs about Caesar in their gatherings. So why do we?
Granted, there is a place to have a degree of sensitivity for those of the "Greatest Generation." Yet "America" is in no way equivalent with either God or the Bible. The historical arc of our country is increasingly becoming anti-Christian.
Far too often in history, the mechanics of persecution have its seeds in seemingly innocuous events. Today, conservatives are upset by those who refuse to stand for the National Anthem. Those who "kneel" are subjected to derision. While context is important, how far are we from an expectation to salute the flag and "pledge our allegiance to it," (can we actually pledge allegiance to a flag/country and God?) as a test of how good a citizen we are?
Christians were covered with tar, tied to poles and set on fire for failing to kneel and call Caesar "lord." It is not a far stretch to have demonstrable expectations of allegiance de rigueur for citizens.
I can see within the next few years the Amercian flag will have no place within the Bible-believing church. Abortion, same-sex marriage, LGBT trends and others will force us to see America for what it is: a nation in rebellion against God and that is nothing more than another tool of Satan.