San Jose, RSL, Columbus, Dallas, probably New England and Colorado might just fold if they were relegated. For other teams the loss of money from media rights and game day profits would likely force them to strip down their academies and have a fire sale on players. I imagine the coaching and training staff would be stripped as well, at which point you would have amateur players coached by amateur teams playing in front of empty stadiums. LA, Seattle, Atlanta, both New York teams and Orlando City have deep enough pockets to survive the economic free fall but I don't think many others do.