Do Americans agree?

I agree. I would add Philadelphia to "worst"-- just for the horrible
food and sickening air quality alone.

Philadelphia is one of the few US cities with a significant history,
and has some great museums. And it does have good restaurants - do you
think a cheese steak sandwich is the only thing you can get there?

Las Vegas is a complete waste of time.

It is the best place in the world for gambling. If you don't gamble,
then don't bother going there.

Chicago IS over-rated, but then I'm from NYC area so it seemed never
that great to begin with.

It is an interesting city architecturally, and has a thriving cultural
scene, and is good for live music also. I wouldn't make it my first
choice of US cities to visit, but I can see visiting if you are in the
general area, have a multiple-flight airpass or are making a
cross-country trip.

You expect L.A. to be bad, so I don;t see that as "over-rated".

It's possible to have a rewarding trip to LA. The famous places
(Hollywood, Beverly Hills, etc.) are disappointing, but if you have a
car and know where to go there are some worthwhile places, for example
interesting immigrant neighborhoods.