I had thought that upgrades didn't count for this (only paid or award F or J). But I could well be wrong in my recollection as I've never accessed a lounge in this way.
Cheers.
Nope. All that matters is class of service when we're talking about "International" (MEX/CentralAm/SouthAm/Europe/Asia/India).
Unfortunately, it gets confusing because of AA's helter-skelter rules about transcon lounge access (that are so heavily dependent upon paid vs. upgraded, two class vs. three class, etc.). So, I can understand why you were confused.