> That, in fact, is what sparked the American Revolution, when the British attempted to seize or destroy gunpowder, cannon, etc. (they did manage to damage 3 cannon).

This is a pretty absurd over-simplification of the causes of the American Revolution. Lexington and Concord certainly involved a British march on militia supplies including weapons/ammunition, but those weapons/ammunition were being gathered not for their own sake, but because of decades of tension over taxation, quartering, limitations on public gatherings, things like the Boston Massacre, etc. leading up to war. The Massachusetts militia weren't just a bunch of gun collectors who got pissed about gun control.

> it is my impression, such bad areas are much more compressed

I'm not sure ghettoization should be pointed to as a success story.