It could be that urban soldiers tend to have more street smarts, and in a war that is being fought in the streets that is a material advantage to survival.
Utter nonsense. Read the Art of War by Machiavelli. The best soldiers come from the countryside. The worst from the city. When I was drafted, I met a hick from the hills of Kentucky. He wore coke bottle glasses which made him look helpless as any other four-eyed wimp I met growing up in the city. At the rifle range, I watch him constantly hit 300 meter targets. It turns out that hillbillies know how to shoot, hunt, and survive.
Kids raised up in rural America are more likely to be inculcated with a love of God, family and country and the knowledge that some things, and some people, are worth dying to protect.
A lot of great American Soldiers, Sailors, Airmen and Marines have come from town, but as a percentage of the overall population, it's the rural kids who answer their contry's call.
I am not sure that American street smarts would be a consistent advantage in foreign cities and cultures, especially after the first month or so.