In large parts of Europe, there are mixed use buildings – shops, sometimes bars, etc lowest floor, and then offices and apartments above.

Add in the availability of public transit, and you can basically always go to whatever bar you wish without driving.

A bunch of trains that don't run after midnight.

Plenty of US cities have 24 hour bus service too.

That's not really a relevant question. The problem is that the "neighborhoods" are too large for there to be a location that's walkable for enough people.

In college students will a mile or several to/from parties or over the course of a night party hopping. Not walking everywhere is more of a social norms issue. In college towns you see many more non-students walking everywhere. People expect people to walk everywhere in college towns and consequently you don't get bothered by the cops for walking around after a reasonable hour unless you're doing something stupid.

In small cities and towns where walking everywhere isn't the social norm nobody does it because walking home from the bar at 2am is likely to get you bothered by the cops because it's not typical.

I would add that for any young female, in any town, walking a significant distance home from the bar after a night of drinking should be avoided.

I wish we could build a world where nobody had to be afraid like this.

That would be like surfing without fear of sharks. If we are going to give alcohol to people, if we are going to allow them to surf, then we must acknowledge that drunk people sometimes do stupid things. Like shark encounters, sometimes those stupid things get people hurt. I don't want to sound like I'm blaming victims, but if we are going to allow people to drink we must acknowledge associated risks. Young drunk girls should not walk home at night. No daughter's father would say otherwise.