On June 26, 2015 the US Supreme Court ordered every state in the United States to license and give legal recognition to same-sex marriage. They cast permanently into the dustbin the centuries old definition of marriage as a union between a man and a woman.
If there was a country that was going to be the first to legalise same-sex marriage it was going to be the US. However, they were beaten to the punch by Ireland whose voters had earlier decided at a referendum to legalise same-sex marriage.