Depends. If they're muslim by birth, but not really religious and pretty liberal in their values, then I have no issues with them. If, however, they are practicing, religious muslims, I don't have a very high opinion of them at all.
The United States could destroy the planet using its nuclear weaponry, but there's no way they could conquer it. There would just be too much involved in trying to keep control.
The bigger question is...what country actually has the desire to conquer the planet? I'm sure it's not the United States. I'd say it's China. They're already trying with India. They keep walking into the northeastern Indian states, and the Indian government is too afraid to face the situation. They make friends with India's enemies, such as Pakistan, and keep building bases in key locations around the subcontinent in order to try and diminish India's influence in that region.