This guy is overthinking (go to the link). You can have allegiance to more than one thing. He says his allegiance is only to God. If he has children he probably has allegiance them, etc.
Having allegiance to America means to me that I support the constitution and I’ll support America when others are trying to run it down.
I am sure that the writer means well, but the implication is that there was some sort of moral failure, when the Founding Fathers pledged to one another, before the Creator, their "lives, their fortunes & their sacred honor."