Only way I could see this happen is if something forced everyone's mind to change.
Anyway, if it happens in an instant, life goes on, I guess, with one less reason for people to hate each other (not saying the world will be in complete peace, because lol it happening at all). Though some people who work in religions with God fields would have to find new jobs... and others continue on as if nothing happened and continue to do "religion", ie corrupt ones who weren't religious in the first place.
--
My Little Phineas and Ferb: Summer is Magic!