If you buy an Apple Watch abroad, these devices are supposed to be used in the country of purchase, due to the different built in hardware, that has to support local carriers, especially if it comes to LTE/5G.
So make sure that your carrier in your country supports this model and all its features.
And the watchOS is also country specific. An Apple Watch bought in the US will always install the watchOS version and all available features for the US. Features that are specific to the US watchOS might not be supported in other countries or missing, in that case.
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copied from: Apple Watch - Carriers - Apple
Also remember, that the warranty for an Apple Watch can be restricted by Apple to the country of purchase.
In case of a warranty claim, you will have to bring the iPhone back to the country of purchase, Apple Support does not ship internationally.
Legal - Apple Watch Warranty US - Apple