One thing to keep in mind is many genetic predispositions aren't exclusive to one specific ethnic set of DNA. Often they are simply found much more likely in said people.
For example
https://www.snpedia.com/index.php/Rs17822931
The body odor and ear wax gene, with three variations
(C;C) 2 Wet earwax. Normal body odour. Normal colostrum.
(C;T) 2 Wet earwax. Slightly better body odour.
(T;T) 2.5 Dry earwax. No body odour. Likely Asian ancestry. Reduced colostrum
There's a reason they say "likely" Asian ancestry (also this kind a shows if you know Asian people who think non-Asians are smelly they may be right lol)... There was indeed early gene flows between different regions such as Europe, Eurasia, and Asia, it was just limited and heavily diffused which makes the traits far less likely though not unheard of.
They include a simple frequency chart... CEU is the best proxy for a typical European American
"CEU - European - 180 samples of Utah residents with Northern and Western European ancestry from the CEPH collection (originally 30 mother-father-child trios)"
As you can see about 75% have CC, wet earwax and normal body odor. About 14% have CT which is wet earwax and slightly better body odor. Only about 1% or so have TT with dry earwax and no body odor.
That means you can in fact be fully European and still come up with non CC variants, it's just more rare.
For example I am a White European American and I come up CT and my mother comes up TT. Mine is fairly uncommon for my ethnicity and my mother's is very uncommon. Now my maternal grandmother's DNA comes up with some Native American DNA from 200+ years ago, so it's possibly that CC Asian variant came through them (if it's an old enough variant) or it just came through the rare chance of European DNA.
Another example that's more mixed is whether you develop more fast twitch or slow twitch muscles
https://www.snpedia.com/index.php/Rs1815739
(C;C) 2.2 Better performing muscles. Likely sprinter.
(C;T) 2.1 Mix of muscle types. Likely sprinter.
(T;T) 2.2 Impaired muscle performance. Likely endurance athlete.
CC being associated with developing more high intensity muscles for things like sprinting and power lifting (fast twitch muscles are the more bulky muscle too so for muscle size)
CT being mixed
TT your fast twitch muscle development is impaired so you develop more slow twitch muscles which are used for non high intensity muscle uses, so endurance etc
The CEU European breakdown is roughly
CC - 20%
CT - 60%
TT - 20%
The biggest outlier is YRI which is "Yoruba African" which have
CC - 80%
CT - 20%
TT - 0% (it seems)
This is why they refer to the CT and TT markers impairing fast twitch muscle development since out of Africa CC seems likely the most common (or at least in Africa) with the other variants developing afterwards.
I happen to have CC... I have distance African ancestry so either I'm just one of the 20% of Europeans who happen to have this variation or it's trace inheritance from my African ancestry.
As far as Asian Flush
https://www.snpedia.com/index.php/Rs671
"rs671 is a classic SNP, well known in a sense through the phenomena known as the "alcohol flush", also known as the "Asian Flush" or "Asian blush", in which certain individuals, often of Asian descent, have their face, neck and sometimes shoulders turn red after drinking alcohol."
(A;A) 4 Asian Flusher; increased risk of esophageal cancer; East Asian ancestry; Disulfiram not effective for alcoholism.
(A;G) 3.5 Asian Flush; worse hangovers; increased risk of esophageal cancer; East Asian ancestry; Disulfiram probably not effective for alcoholism.
(G;G) 2 Alcohol Flush: Normal, doesn't flush. Normal hangovers. Normal risk of Alcoholism. Normal risk of Esophageal Cancer. Disulfiram is effective for alcoholism.
In this sampling the Europeans had all GG, though even the Asians weren't all positive for the Asian Flush variants.
One thing to keep in mind is that this doesn't mean zero Europeans have AA or AG variants, just that's it's probably very rare. The sample sizes for these tests only show so much.
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. There have been times in my life I have too, even if it hurt like a mofo. I won't now that I know it causes esophageal cancer for people with AFS: 
