"Urban centers are not all violent. You're finding a false correlation to avoid facing a fact you don't like"
they're urban centers in the united states, however, so they warp the standards. one of the most dangerous places in europe is mälmo, sweden, and even that's safer than anywhere in america.
"Warsaw is a city of 1.8 million, but has a murder rate much lower than many major U.S. cities."
and surprisingly better infrastructure for a former communist nation
"Hmmm, what do you think might differentiate Warsaw from, say, New Orleans"
climate and being in florida's vicinity.
infrastructure-wise, new orleans is a city divided by freeways, while warsaw has a world-class tram network. warsaw has consistent intercity train service to krakow and gdansk, while new orleans has a daily (currently thrice-weekly) amtrak to atlanta. in short, connectivity and accessibility to the entire country has made different parts of poland hate each other less. meanwhile, the united states can't get over living in the same country as alabamans. this argument also applies to the balkans, a particular region in europe with poor infrastructure.
history-wise, the southern united states has a longer history of african slavery than europe has, while poland didn't even exist for a span of time until world war 1 ended.