Loyalty is an organic thing. It either grows as a natural product of our socialization or it doesn’t. When children were raised in the Judeo-Christian American culture that used to prevail, their family, religious and community values were all in harmony with American ideals of fairness, equality, hard work, self-reliance, duty, self-sacrifice, virtue, faith, charity and patriotism. No oath can compensate for these values, if they are not inculcated and, nor can it overcome values hostile to American ideals.
Without intending to, I think I may have just described what makes the American left so strangely similar to Islamists. Although they are culturally worlds apart, they share disdain for American values.