Why do you suppose God told us why there are different languages but not why there are different races? The different races is an argument atheists use for evolution.
Noah’s 3 sons each had distinctive physical features, and all the different races developed among their descendants. I believe when God confused the languages He didn’t do it randomly, but by people group. This means people from specific tribes or clans were given a common language that people from other groups could not understand. As these groups separated from each other marriages within each tribe or clan produced children with the dominant characteristics of the clan. Over time these dominant characteristics became even more pronounced.
You can see this today in the fact that people from particular regions of the world share physical characteristics that are remarkably different from people of other regions. This is especially true when opportunities for intermarriage with other groups has been limited. Research by scientists has demonstrated how the different races could have emerged within just a few generations.
By the way, the different races really present a strong argument against evolution, not for it. Any dog breeder will tell you that the way to protect and enhance a particular line’s unique characteristics is to prevent breeding outside the line. But if you put all the dogs together and let random selection prevail, pretty soon all you would have is a bunch of mongrels. It takes the application of an intelligent outside force with a specific purpose in mind to prevent mongrelization.
This brings to mind something I learned a while back on the different approaches taken by believers vs. unbelievers is cases like this. The believer asks, “How did God do that?” and through study discovers there’s an answer that explains it. The unbeliever says, “God couldn’t have done that” and looks no further. Maybe God didn’t just tell us about different races because He wanted us to discover it for ourselves as confirmation that the confusion of tongues happened the way He said it did.