I doubt that the baggage check restriction is from US regulations. I've checked bags to and from the US with multiple transit points on both ends with little problem in the past. PVG is the only transit point where an agent told me flat out it wasn't possible due to local regulation.

Looking at historical times for AA182, delays of 30min+ aren't uncommon. Hopefully delays of >2hr are rare, but with any overseas flight with a single aircraft turn, it's not out of the question.

If you need to recheck bags, I don't see any need to collect boarding passes separately. It's not (like the US) where you can drop bags after customs without a formal recheck - you must recheck with an agent anew.

However, if you had no checked bags - I presume immigration/customs clearance isn't necessary, provided that there is a transit desk and transit security? Can anyone confirm this, or do all/most transits require immigration and customs clearance?