I don't think you did anything wrong or anything that would warrant the suggestion of racist treatment, but I don't totally agree with the above either. Racist treatment isn't always direct and obvious, especially in customer service. Some racists might refuse to take the table, but some wouldn't. And a waitress doesn't have to be KKK-level racist to treat customers differently based on race.
I still remember going to a chain restaurant when I was a child that we basically had to boycott because we experienced what my dad perceived as racist service. It was a restaurant we'd been to several times before. Party after party got seated while we waited and waited. And who knows? Maybe there was some reason, like those parties had one person more or fewer than ours. I don't remember the details because I was too young. But I also know that my dad isn't likely to imagine these things. Racism in restaurants can be subtle.
But, again, I'm talking generally. It doesn't sound like you did anything unusual.