The Apple Watch Series 11, Apple Watch Ultra 3, and Apple Watch SE 3 all feature an upgraded 5G modem and antenna architecture, but 5G connectivity won't be available in some countries.
5G is not listed as a supported feature for the new Apple Watch models in Canada, Australia, New Zealand, Brazil, Mexico, Saudi Arabia, and several other countries in Europe, South America, Africa, and Asia.
The upgraded connectivity is available in the United States, UK, Germany, France, Switzerland, Spain, UAE, Thailand, Japan, China, Singapore, India, and more.
It is not clear why 5G connectivity isn't an option in some countries, but it could be due to a lack of regulatory approval or carriers that simply haven't added support. During yesterday's event, Apple showed a slide with carriers that are supporting 5G on the Apple Watch at launch. These were the carriers depicted:
Canada's major carriers like Telus, Bell, and Rogers were not included, nor were Telstra, Vodafone, and Optus, which are the three main carriers in Australia.
You can go to the technical specifications page for the Apple Watch Series 11, Apple Watch Ultra 3, or Apple Watch SE 3 in your country to see if 5G will be available. In areas where 5G is not listed as a feature, the new Apple Watch models will rely on LTE.
Source: Macrumors