Due in part to the three Abrahamic religions, Judaism, Christianity, and Islam, the doctrine of Monotheism is known around the world. This doctrine states, in simplicity, that there exists only one God, that no other being exists in the same stature as this God, and that no other being requires our worship and praise as a God. The literal definition of the word is made of the Greek words "monos," meaning one, and "theos," meaning God. In short, it means "one God." In the United States, the notion of Monotheism is incredibly popular. What many politicians deem as "Judeo-Christian" values have, at their very core, the notion of Monotheism and, despite current political views, Islam is not excluded from this notion.
According to the logical conclusion that exudes from monotheism, only one monotheistic interpretation can be the correct one, since there can only be one God. All three of the Abrahamic persuasions hold that they have access to the ultimate truth and all three of them, at their Orthodox levels, are of the belief that they are the only ones whose God exists. According to these faiths, the message that God sends is the only one that we, as humanity, should be paying attention to.
This is directly in contrast with the famous American value of tolerance. If I were to accept a Christian Monotheist’s position that there is only the Christian God, then I would be rejecting the Muslim notion that there is only the Muslim God. Likewise, if I were to accept that there is only the Jewish God, I would be rejecting both the Christian and Muslim Gods. There is no possible way that I can choose a Monotheistic interpretation of one God without being in the wrong according to a different Monotheistic belief. This isn’t a debatable fact about monotheism, there cannot be more than one God according to monotheism.
Now, their beliefs don’t necessarily correlate with violent and intolerant actions. That would be the decision of the individual monotheist to interpret his or her monotheistic belief into action. However, there is still the underlying notion that their persuasion is right, that what they believe is the only correct way to believe, and that everyone who doesn’t believe what they believe are on the "outside" while they are on the "inside."
However, then there are those who can’t separate their intolerant beliefs with their actions. There are people who are so fueled by the notion that their monotheistic persuasion is the correct one that they cannot step out of their beliefs for a single moment and live among the rest of the world. Often, these radical monotheists go to great lengths to attack and cause distress not only to those within their own religion, but also to other people who do not share their beliefs. Since they believe that only they are correct, anything that they do in defense of their notions are correct due to whatever they believe is the metric of truth and justice, since their persuasion is lead by a perfect God.
According to the very nature of monotheism, the notion of "I believe what I believe and you believe what you believe and we are both right in our way" is demonstrably false. Monotheists have to believe that only their notions of God are correct and that everyone else is incorrect, otherwise they are engaging in cognitive dissonance. This isn’t a bad thing, however, just an irrational one.
Perhaps it is the peculiar nature of this country to have such a strong force of Monotheists. However, people who engage in violence in defense of their monotheism are seen as on the fringe, even by their fellow monotheists. This means that the overwhelming majority of people can put aside their monotheistic persuasions and their singular worldviews in pursuit of the common brotherhood of man. It could be that the apparent contradiction between monotheism and tolerance is simply one of belief and not one of action. While someone can hold the belief that they have access to the ultimate and eternal truth, they won’t act violently on that belief when they encounter others who reject it. That could just be what makes this country so great. Call it cognitive dissonance, call it irrational, or call it the American Melting Pot.