Hello rel866, welcome to the Samsung Community! I understand your concerns about you not being able to connect to the Samsung Health app due to it showing "not available in your location". You stated that you purchased both devices in the US and your phone from T-Mobile, but where did you purchase your watch? You can clear the cache to the Samsung Health App, and also you could try uninstalling/reinstalling the app.
To clear the cache: Open Settings, Apps, find the Samsung Health App, Storage, Clear Cache
