Is Same Sex marriage good for the U.S.?

I would have to say overall "Yes" within the 50 states. But, not outside of countries who have also voted in Same Sex marriage.

The main reason I think this is good is less people will kill themselves because of gay issues. So, generally speaking people who are gay may be happier and better financially protected by the government when spouses die, for example.

There are a lot of issues around this that haven't been dealt with though, because for Muslims and Christians, this is a sin against God for those who take this seriously in their lives. So, you might have violent acts still perpetrated against the Gay and transexual community by extremist Christians and Muslims in the U.S.

But, generally speaking, if I look at all 50 states this will tend to prevent a lot of deaths and unhappiness in the U.S. by allowing all people to marry and not just some of them. Equal Rights.

And then also, one could look at the Bible and think: "Why was homosexuality thought wrong?"
The main reason was no children could result.

However, in a world of overpopulation (just like Charleton Heston in "Soylent Green") being homosexual might reduce the number of children born and be a hedge against overpopulation too worldwide.

However, that doesn't seem to be the direction this is all going now which might also lead to other social problems down the line as of yet unseen by most people.

So, the best way I think to look at this at present is it is a social experiment that could succeed or it could wind up biting society in the butt in ways not yet fully understood by the world.