I assume this is for domestic travel? AA's equivalent of POUG is available from airport kiosks only, ranging from $50 to $250 depending on distance. It is offered to Avios bookings, but the chances of it happening on the longer sections are quite slim due to the nature of AA's frequent flyer programme. You'd be in with a chance for shorter sections or off peak. No addition Tier Points or Avios accrue from the upgrade, whether the underlying fare is cash or Avios.

Having said that, for middle to long sections I personally think using Avios is a great deal, the fees are very low and you get a long time in the air per Avios. So I'd certainly think of ways of creatively boosting my Avios pile for that specific purpose.

For international travel the chances of an upgrade offer are vanishingly small if you don't have status with AA, but they do happen.