The EU does passport checks on many internal travel services. It's not that there truly are no ways to travel without showing passports, but there's very few. Well on the continent you can just take a car, although with the refugee crisis there's many checks.

E.g. taking the train from London's King's Cross to Paris you will be subject to a full security screening and passport inspection. Faster than getting on a plane. Same for taking internal flights (even within a country. Paris to Marseille ... you need a passport) and I'm sure that's not the last list.

I contend that despite this there are many differences between the EU and the USSR, even with both being led by "commissars" (or is it commissioners ?)

That's because their passport was a universally accepted ID and just about everyone had one issued once they turned 16 (I think it was mandatory to have one actually).

Except that in the USSR the checks existed because many people simply weren't allowed to travel, you can still take other modes of transportation without a passport, and this passport requirement has a roughly zero chance of actually happening.

I'm no fan of the airline security apparatus, but let's be realistic.

I had to show id card for the Barcelona - Madrid rapid train. Spain is as far from USSR as possible.

In Europe the system with population wide government mandated and granted id works very well, is not burdensome and is not a big deal. And I have no idea why the US has not implemented one yet.