Spot on analysis, Mr Optimistic. Your account is exactly what I have experienced with these shambolic US legacies, and American and United are no different.
BA and VS are light years ahead on service, and I am not saying this because I am anti-US. Far from it. I would love to see Jet Blue going trans-atlantic and really shaking up the market.
If you have to fly economy again, also consider Norwegian, which has a very good (so I hear) premium product which is only slightly more expensive than the legacy economy fare. They fly to 5 or 6 points at the moment including New York, Boston and LA and are steadily expanding.