For those of you bemoaning how "backwards" the U.S. is, of roughly 206 countries 13 (15 in August) allow same-sex marriage, that's 7.3%. Even in progressive Europe, only 22 of 51 countries recognize any same-sex union, with only 9 allowing marriage or 17.6%
The U.S. also has multiple avenues for rectifying inequality under the law. It is possible that two Supreme Court rulings this month could make same-sex marriage legal under the Federal government and/or require all states to recognize gay marriages. This will take effect immediately after the ruling, much faster than what is happening in the UK. Also, keep in mind the House of Lords is based on peerage dating back to the feudal system and also has dedicated spots for clergy, whereas our dysfunctional congress is at least elected.