i doubt some random thing will trigger people in america to go insane. plus why 7? and do time zones count? if it's 7 PM in New York, will people in LA go insane too, or will they have a 5 hour window before crazy? [see, this is why The Purge wouldn't make sense people lol]
in all seriousness, America is at a turning point, there's no prophecy to blame, it's a long time issue that's reaching the breaking point. one day there might just be a giant riot because of all the problems, and it may seem daunting, but you have a choice. instead of hiding inside, perhaps you might wish to join people helping your community, or fighting for causes, or something to resolve the issues so a 'day of rage' doesn't happen.