> Given that the US military uses up 250k rounds per killed insurgent

I'm willing to bet that average engagement ranges in street violence in the US are closer, and the involved parties less effective at using cover and concealment, than is usually the case in battles between professional modern military forces and insurgent groups that still exist after several years of ongoing combat with professional modern military forces. Also, the weapons used are different.

So, generally, I wouldn't use statistics for the latter as a yardstick for evaluating shots/victim ratios for the former.