The nationalistic litany proves to be the opposite of the sense of “to bless” as used in the New Testament:

Mixed Blessing at inward/outward
Of the 41 appearances of the Greek verb eulogeoo (literally “speaking a good word”), only twice do we find it in the imperative mood. In neither case does it involve God. It does, however, involve us. Jesus invites his disciples to “bless those who curse you” (Luke 6:28). And Paul later echoes those words: “Bless those who persecute you, bless and do not curse” (Rom 12:14). Sadly, even many churches endorse the nationalistic slogan, oblivious to this remarkable scriptural cue.
—Ched Meyers, from an article in The Other Side , December 2001

Speaking actually of the radical love as lived by Jesus, working against the ethos of revenge, “God Bless America”, as an imploring to God to give us “victory over our enemies” could not be further from the Biblical message. Such is the “foolishness” of God.