Pledge of Allegiance is Intended as a Religious Statement

Many don't realize that the Pledge of Allegiance did not originally include any references to any gods. The phrase "under God" was only added in 1954 as part of an effort to better define America as a godly, religious, Christian nation as opposed to the atheistic communism of the Soviet Union and allied states. The addition of "under God" was thus always intended as an endorsement of particular religious and theistic beliefs and that's how it was perceived at the time. Opposition to the Soviet Union was important, but it could not justify trying to define America along religious lines or telling Americans that patriotism must be linked to particular religious or theistic beliefs.

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"Under God" Promotes Belief in a Particular God, Not Theism Generally

Far from being a general endorsement of a vague sort of theism, "under God" in the Pledge of Allegiance endorses belief in and particular attitudes towards a particular sort of god. First, it's "God" which is the designation of the monotheistic deity of traditional western religions — Christianity and Judaism in particular. Second, the phrase indicates a special relationship between this god and the nation, a blend of religion and nationalism which not even all Christians accept. The early Deists, for example, believed in a God who created the universe but then stepped away from it and did not intervene in the affairs of humankind and certainly didn't provide any special cover for any nations in particular.