Jews don’t hold by American law in such matters – so it doesn’t affect us. By halacha, our law, one is no more allowed to marry a person of the same gender than is one allowed to marry a non-Jews (BTW, Anglo-American law has allowed Jews to marry goyim since the late 1700s).
By decriminalizing various of forms of non-marital intimacy, the goyim did a lot more violence to the concept of marriage than in allowing people who by definition are incapable of bearing children to marry. And those changes occured in the early 20th century, or earlier.
The only danger is that as marriage is increasingly defined a a couple, rather than a couple with children including a usually dependent spouse, the many laws that benefits families will no longer be justifiable (e.g. the tax break for families with one spouse earning much less than the other, which also works as a penalty for spouses with equal incomes).