Country & State Abbreviations in URL

My directory is focused on US and Canada. I’d like to display full country names on the site but use US and CA in urls. I know I can translate the country name via the PO file but I didn’t see any way to just change it to the abbreviation in the URL. Is that possible? (By the way, on the MultiLocations Translate Countries tab it would be helpful to add a note that countries are in the *core* PO file. I first downloaded and setup the mulitlocation po file before I realized where they were.)

I have a similar question for states. Is there any way to enforce use of abbreviations on the site and urls, or just in urls?