I do not believe that that is currently a feature in AppMon. I did a search for how you might achieve this with regex alone, but that did not yield any favorable results.
You could submit this as an RFE (request for enhancement) as I am certain others would benefit from this feature as well.
Otherwise, you'll have to talk with the dev team for the app to change stuff like usa-en to USA, so that AppMon can capture the string that your customer wants displayed.
Hope that helps,