Apple watch

If you just want a GPS only Apple Watch it should work anywhere. If you want Cellular you need the version for your country because of the cellular radio frequences used in each region.

If you are getting the Apple Watch in Argentina, then start here (I think this correct but I do not read Spanish, so I could have this wrong) <https://locate.apple.com/ar/es/>

If you are going to purchase in another country, such as the U.S. when visiting here, you would look up a local Apple Store, or order it so it is delivered to where you are staying while in the U.S.

The Apple Store link provided by BobHarris appears to be good for local purchase in Argentina. Be aware that in most countries Apple only sells within country, and orders to be shipped to export destinations are not accepted. You can of course walk into an Apple Store anywhere and purchase over the counter, but they will not ship online orders out of country.

(Edit: when I look closer at the link it appears Apple does not have a direct presence in Argentina, only authorized resellers and Apple Watch is not listed. You may find the only way is to travel to another country, or have a trusted friend take delivery and forward your new watch)

If you were thinking of buying the cellular version of Apple Watch please be aware the Argentine networks do not yet support service for watch (see Apple Watch - Carriers - Apple) so you would have to use it in non cellular mode linked to your iPhone like the GPS only version. Also be aware that even if (when) your network launches support a cellular watch purchased in USA will be incompatible with your network in Argentina.

A watch purchased outside of your country may not be compatible with your carrier(s).