As has been pointed out by others, most Muslims around the world are not a problem, and the same is true for those in the U.S.
But the problem with Islam is, if you take it seriously you will be a cancer in any society, even the ones that are majority Muslim. Add to that, the teachings that seem to encourage atrocities (death penalty for homosexual acts, for leaving Islam, allowance of wife beating, etc.), and it does not take a high percentage of Muslims - current estimates are that there are TWO BILLION of them on Earth - to make them a pox on humanity. They DO NOT believe that "all men are created equal." They DO NOT believe that religion should be subordinate to the state. They DO NOT believe in freedom of expression for all. They DO BELIEVE that it is OK to lie, deceive, reverse commitments when it suits their interpretation of the circumstances. In Muslim countries, Sharia courts can countermand clear provisions of contracts because they deem them unfair. Is it any wonder that no western investors will develop anything in Muslim countries?
So if only ten percent of them take their religion seriously, that's 200 million crazy bastards.
It would be entirely rational for civilized countries to either reject Islamic immigrants outright, or demand an oath of allegiance to the prevailing culture before allowing them in. This is one reason why Germany is preparing to eject about 800 thousand Syrian asylum seekers. They are a cancer.