We could argue a long time about what counts as "mixed" or as a "race", but there are definitely genetic clusters[0]. I don't think it's that surprising given fast travel is a relatively recent invention. The clusters will probably become less distinct over time.
The point I’m trying to make is these genetic clusters are from a particular snapshot of time when we decided to classify these. Each of those clusters is already a combination of a smaller number of clusters that would have existed in a previous snapshot. And I’m not talking about a snapshot from prehistoric times more along the scale of a few centuries.
>these genetic clusters are from a particular snapshot of time when we decided to classify these
Not even. No 'races' as commonly understood are defined based on a snapshot of genetic clusters. The concept predates modern genetics or knowledge of DNA. Races are complex social constructions based on appearance, language, ethnicity, etc. etc.
[0] https://commons.wikimedia.org/wiki/File:Principal_component_...