If America defaults on its debt, would American citizens starve to death and the world completely collapse?

Top US experts like Gerald Celente have said that if the debt ceiling isn't raised, we are going to default from lack of money cuts, which will turn us into an underdeveloped nation into a third world country just like Zimbawe.....is this true??, or will things get better like always, just like grandma says../ idk, im freakin out, please give FACTS!!!!!!!!!!!!!!