Its a little different , because the population is higher , and unimaginably higher , if lets say you have situation like no bread in super markets or food is not present , and economy fails
Their would be chaos like POST Katrina as there are huge number of blacks and Latinos now living in USA , before it was just few migrants and Americans etc
So when there is no bread or food or oil in country - what do you think will happen ?
Yep every one will blame the black and Latinos and then all chaos will break lose
Likely the Rich , will try to secure the oil centric states , and the poor Americans will try to revolt to save their homes , so there would be major power struggle at some point for sure
A few migrants? Its a nation of immigrants. Germans, Dutch, British, French etc. Japanese, Chinese, Mexican, African it don't matter.
Most likely nationalism will rise in Europe and Asia first and then war starts somewhere around those places and the U.S. provide weapons which means jobs at home. If isolationism takes effect.