Old concern, but it really doesn't work that way. Genetics don't respect human ideas like "nationalities" or "borders" - the targeting you can get by selecting on singular DNA variants is coarse enough to make ICBMs look like precision weapons.
Like many things of this nature, people keep bringing it up because it sounds Very Scary and Very Dystopian - not because it's worth giving an actual fuck about.
If it's year 2126, and you have this kind of tech floating around, and you aren't equipping the entire population with artificial immune systems capable of dealing with known and unknown biological threats? You've done something wrong.
Like many things of this nature, people keep bringing it up because it sounds Very Scary and Very Dystopian - not because it's worth giving an actual fuck about.