Mega cities are a lot more efficient and I think most people would rather live in one than a small town.

And they're actually easier to protect because you can build all your bunkers, barracks, drone bays and ABMs close together. The attack surface is a lot smaller. In less urban countries you have to decide what needs protection, and if you guess wrong more people will end up dead.

We should be decentralized in terms of power, not geographic distance. A city where everyone has a gun and military training is much harder to attack than 100 villages with the same total population. The important thing is making sure that even if the city falls theres a plan to avoid civilian casualties, and the rest of the country is independent enough to work without it.

If that were true then everyone would have centralised their industry in WW2 to make it resist the bombing. They didn’t, because having one small target is way worse than having dispersed targets.