Check out this neat little graph which compares public support of same-sex marriage and interracial marriage. I'm not sure what exactly explains this difference, but Americans were much quicker to endorse same-sex marriage than they were interracial-marriage. Maybe in the last 25 years the US has become more progressive on many fronts? Or maybe this is another sign of the way racism is still entrenched in American society? Good news is that interracial marriage has been legal since 1967 (though that took way too long!) and the recent Supreme Court decisions are continuing to pave the way for same-sex couples to have full legal access to marriage.
It took nearly three decades after the Supreme Court legalized interracial marriage across the country for it to reach majority approval in the US. But same-sex marriage has maintained popular support, according to Gallup, since 2012 — before the Supreme Court struck down the federal ban on same-sex marriages and effectively enabled court rulings that have ended more than a dozen states' marriage bans.