This is a common myth with no basis in historical fact. The Encyclopedia of Wars (Philips, Axelrod, 2004) attributes only 7% of wars from circa 3,500 BCE to the present (albeit 2004) to religious reasons (half of those being Islamic). In other words, 93% of major wars, rebellions, and revolutions are secular in nature. There are ways the critique the way the Church has followed Jesus, but this is not one of them.
This is misleading because it lumps rebellions and revolutions in with wars. The reason more rebellions are secular is that there aren’t many theocracies.
This is further misleading because religion is politics. In the United States, for instance, nobody would pin the Civil War on Christianity. But, was there a Christian component? Of course. The Southern Baptist Church formed in 1845 when the Baptist Church in America became abolishionist; the Southern Baptist Church was anti-abolitionist (a political stance, and a reason for the Civil War). This allowed white Baptists in the South to remain nominally Baptist and later participate in the Civil War. All of these forms of Baptism are recognized as legitimate denominations of Christianity today.
So, even if religion didn’t drive the American Civil War, it certainly played its part. It still does today in the ‘War on Terror’ and ‘War on Drugs.’ Maybe you don’t consider those wars. But, people are dying, and fundamentalist Christians (among others) are still stoking the fires of conflict for their own political reasons.