Not a single person of size is in this movie other than Henderson/Sammy. The idea of Americans being physically fit enough to conduct proper sectarian violence in urban environments is less believable than the narcissistic journalists, two of which have girlboss syndrome and one which was a literal teenager, being allowed to "embed" with units without any PPE and constantly get in the way of active combat operations.
The entire premise of an overweight nation of doordash, netflix and substance addicts reenacting Fallujah across major American cities is laughable at best. Many of these people with decked out armalite and magpul gear can't run a mile.
It's a shame since Garland has made better movies before (see: 28 Days Later, Dredd), which were much more immersive and convincing.