Apple Watch Cellular capability for Americans living overseas

Hi

Apple Watch Series 3 (GPS + Cellular) is not locked to any specific carrier and has a built-in eSIM that copies information from the iPhone's SIM card.

The built-in cellular features require a carrier plan for your iPhone in your country of use that specifically includes support for Apple Watch Series 3 (GPS + Cellular), including the carrier activating the device on the plan.

If buying Apple Watch Series 3 (GPS + Cellular) in one country to use in another, then, in order to use the built-in cellular feature, you would need to buy a model that supports the relevant LTE and UMTS bands for your intended country of use and your supported carrier there.

There are three different regional versions of Apple Watch Series 3 (GPS + Cellular), each supporting different LTE and UMTS bands, as detailed here:

Apple Watch - Carriers - Apple

If in doubt, I suggest that you contact your preferred intended carrier to ask whether any given model can be used on their network with a plan that they may offer or plan on offering for iPhone that supports Apple Watch Series 3 (GPS + Cellular).

Apple Watch Series 3 (GPS + Cellular) can also be used without activating the built-in cellular feature, in which case it functions like a GPS-only model.

The built-in cellular features cannot be used when roaming. Also keep in mind that warranty service availability may be restricted.

Hello!

I've found this link which pretty much answers your question:

Apple Watch - Carriers - Apple

Hope I helped!