Changing Your Apple Watch or iPhone's Region Won't Enable ECG App Outside of United States

Apple today released watchOS 5.1.2, which enables the ECG app on Apple Watch Series 4 models. However, as Apple made clear, the ECG app is currently only available in the United States and its territories of Puerto Rico, Guam, and the U.S. Virgin Islands, preventing it from being used internationally at this time.
Many software features on Apple devices are initially limited to the United States, but international users have often been able to simply change their iPhone or Apple Watch region to the United States to gain access.
That's not the case with the the ECG app on the Apple Watch Series 4, though, as it only functions on models purchased in the United States. Those who live in and bought an Apple Watch in Canada, the UK, or elsewhere abroad can't use the region-switching trick to enable the ECG app — it doesn't work.