Biological weapons are problem already. Too easy to make, too deadly to use, and harder to regulate than nuclear weapons...
Ethnic cleansing using biological weapons is unlikely, simply because it is complex, making common cold more lethal is more likely. It is obviously a reason for regulations to exist on international level in the first place....
Rest is not much of the problem. Gene modding is bound to be complex, and prohibitively expensive, require an advanced technology, with no immediate benefits, which means that modding the rich elite or future child soldier would be done only in very rich countries which are unlikely to be sanctioned by US in the first place - more like US, less like North Korea. Which isn't something you are worried about.