Actually America is not overwhelmingly christian.
There is a large number of christians, yes, but not overwhelming.
You see, many Americans are christian in name only, by such I mean that their parents claimed to be christian, but other than for weddings never set foot in a church, and while there may have been a Bible in the home, no one ever bothered reading it. There are in fact generations of so-called christians that are no more christian than they are communist Chinese.
A christian is defined by more than a belief in a single deity, one that is male. Several religions follow that belief, so simply declaring a belief in God is not enough. A christian is expected to attend services, at the very least on high holy days, such as Easter and Christmas, but many that claim to be christians do not go to church at all. A christian is expected to live in a prescribed manner, outlined by the Ten Commandments, the Book of Proverbs, and the teachings of Jesus, but they do not, in fact they have little knowledge of those guidelines.
Very few "christians" have any knowledge of any religion. Often their ideas of spiritual discipline are more closely related to other religions.
The claim to christianity by far too many is no more than superstition-based.
Religion, incidentally is defined as "spiritual discipline." Perhaps the path you follow is not the best path to train your individual soul.