We are visiting our friends in the US on vacations and would like to get married while there, but neither of us are citizens of the US.

Which states allowing same sex marriage in the US for two foreigners on vacation? I found lots of states which allows same-sex marriage for the US citizens, including: Massachusetts, Connecticut, Iowa, Vermont, New Hampshire, Washington D.C., New York, Washington, Maine, Maryland, California, Delaware, Minnesota, Rhode Island, New Jersey, Hawaii, New Mexico, Oregon, Pennsylvania, Illinois. But it is unclear is it possible to do get married in case we are both non-citizens (citizens for some other country, not the US)?

How long should it take to do that (if there any waiting period between applying for a license), how much it'll cost and which countries will recognize it?

How to contact the UK government to find out all the details?

The same question regarding the UK here.