Its clear that the US wants to oust Assad from the very beginning. It did the same with Saddam Hussein in Iraq and Gaddafi in Libya as most recent examples. If this starts at a nuclear war - not only innocents will get killed but it would also called irreparable damage to earth which is already in grip of global warming.
Laybia and iraq is just what the public is aware of there is so much more to it , they also tried to aust Edagon the biggest enemy of the world are not the Nuks but rather the United States and its ego.