There is more to 'the world' than America. America was an aberration for legislating marriage so closely. Consider that someone in India in the 1800s would have thought that caste simply 'was', whereas the rest of the world would have been shocked by it. Similarly, anti-miscegenation laws, while common in America, and easy to think of as 'normal' from an American perspective, were not that common. Almost every culture normally socially approved of a man taking on a foreign wife, and most cultures welcomed foreign men who adapted into it marrying a local woman. There are countless examples from almost every part of the globe. It wasn't exactly uncommon. For the last two thousand years, the largest religions on the planet, would have supported a man and woman of different races to be married. Neither Catholicism nor Orthodoxy nor Islam nor Hinduism nor Buddhism (which together constitute the vast majority of the world) would have ever had any issues with interracial marriage. In fact, they would have encouraged it against a non-believer of the respective traditions. Not a single one would have supported gay marriage.