Re: Would someone explain
It's even more complicated than that -- it varies from state to state whether the whole intersection is covered, or if you just have to clear the stop line before the light turns red.
Also, stopping *in* the intersection (because you tried to cross it before there was room on the other side) is its own offense, "gridlocking," in some places. California has had a whole (mostly ineffective) "don't block the box" PR campaign.