Just like it didn't happen over night in countries that do have gay marriage, and the like. Sadly it takes time. And we in the US are not alone in this fight.
Actually it did practically happen "over night" in Spain. The war in Iraq was going badly, the train bombings...a sudden and unexpected change in government and out of the blue (practically) same-sex marriage. Gay Spaniards were shocked it happened so fast, as the straight ones were. We are talking about months here, not years.
Changes in smoking laws in Spain likewise came "over night" and out of the clear blue sky.
Just a little factoid.

