Both USA and UK have a sizeable subpopulations of people of European, African and Asian descent, large enough to have reasonably reliable statistics on them.

I kinda expect it's just not possible for two main reasons:

- the concept of "race" ("ethnicity" would be a better word?) will vary depending on culture, and the intial split of populations + 2 centuries should be enough to bring significant divergences. When you say "asians" I'd fully expect the composition of that group to be a lot different on each sides of the pond.

- I don't expect the UK to have widely available etchnically separated data. They do check the repartition on census, but would they refer to that on death stats ? I could be wrong but that seems complicated on many aspects.