Are accents cultural or racial? There's plenty of cultural traits which are heritable and measurable. The difference is that there's only one human race, while there's many different cultural memeplexes.

Race literally doesn't exist: The partitions that you imagine as dividing people aren't actually backed by any particular observable or experiment. Meanwhile, cultural markers do exist: We can measure what people wear, speak, trade, value, etc.

Aside from accents, another good example is that of locally-grown staple foods. Different locales support different crops, so that merely living in a region for a time is sufficient to alter one's diet. Yet it is not due to differences in people, but differences in soil, which determine which crops are grown and eaten where.