Who do you serve, your country or your Savior?
Most American Christians I have known are primarily Americans, and secondarily Christians. Their foremost loyalty and allegiance is to the American flag, their nation, that "great country" that they seem to believe has given them everything they have and has given them the opportunity to enjoy all they've got, and their "freedom."
When Jesus preached to the Jews about freedom (see John 8), they said, "we've never been anyone's servant...." They didn't see the need for any liberation, because they thought they were already free. But Jesus said, "I am telling you the truth: whoever commits a sin is a servant of sin."
The sad thing is that a lot of Christians merely use their religion as a cloak for their sin; a cloak to hide it, especially from themselves. The rest of the world isn't that easily fooled, because most of us can tell real righteousness from hypocrisy, true faith and saintliness from mere disguised selfishness and self-adulation.
It's what C.S. Lewis called the universal moral law, which Paul also described in his epistles, as doing those things which are lawful, even when we don't know the law, while others, claiming to keep the "law" are often its greatest violators.
Now let's expose that sin of nationalism. What's so bad about being a patriot and at the same time claiming to be a true Christian? If Christians would read their Bibles a little more, instead of just listen to the pre-chewed versions of what the Bible supposedly says, from their TV-evangelists and preachers, they would know. First of all, Jesus said to His disciples, His followers, those who adhere to His teachings: "You are not from this world." (John 15:19). John takes this further in his epistles and says, "If any man love the world, the love of the Father is not in him" (1Jn ), and James even says, "friendship with the world is enmity with God" (James 4:4).
So, since your country is evidently a very visible and tangible part of the world (and not only that, but in most patriot's mind, also the best in the world, and "champion of the world,") you're going to have to make a decision whom you're going to serve, and who is your master, since Jesus said you can't serve both.
Most American Christians justify any criminal action of their nation against another by the mere fact that if they're a Christian nation, so that whatever they do, whichever nation they fall into and breathe slaughter against, it can't be wrong. But that attitude is in itself very wrong and is based on the grossest of collective self-deception that human history has probably ever seen.
A true Christian and a true believer is one of those described in the 11th chapter of Hebrews, where we find a list of all those great pilgrims & strangers who refused to call this world (and any nation in it) their home, because they were seeking for a better Place, Whose Builder and Maker is God.
So, when it comes down to it, I strongly disagree with anyone who says that they can be a devout patriot and a true believer, a real Christian, at the same time, but I will even call every flag-waving patriot pretending to be a Christian a hypocrite and a traitor.
There were a lot of Christians in the 3rd Reich under Hitler, who swallowed the baloney that Adolf was supposed to have been a Christian & this figured that God was on their side and whatever Hitler did couldn't be wrong. Some people have pointed out the striking similarity between Germany toward the beginning stages of the 3rd Reich and the Bush administration, and I think they're right, though Bush wasn't the first American president whom some compared to Hitler (- a little insider quiz on the side: Who was "Nitler?").