Explaining in detail, since there's a lot of misinfo in this subthread.
The new georestricted iOS features, like 3rd-party App Stores, are behind feature flags that only activate in certain regions. There are multiple factors taken into account when determining whether a flag should be activated. They include GPS location, location obtained from nearby cell towers, the issuing country of your SIM card, the region you set in settings, the country that nearby WiFi networks broadcast for regulatory purposes[1], and (indirectly, through the billing address) the issuing country of the credit or debit card that you use in the App Store.
Not all of them have to match, but the threshold is high enough that you're very unlikely to meet it while physically in the US.
Feature flags stay activated for 30 days since last eligibility, so if you're an EU resident and leave for a vacation, you're fine. If you traveled here as an US resident, you (probably) could get these features activated, perhaps needing an european Apple ID and/or SIM, but they would only stay on for 30 days.
The new georestricted iOS features, like 3rd-party App Stores, are behind feature flags that only activate in certain regions. There are multiple factors taken into account when determining whether a flag should be activated. They include GPS location, location obtained from nearby cell towers, the issuing country of your SIM card, the region you set in settings, the country that nearby WiFi networks broadcast for regulatory purposes[1], and (indirectly, through the billing address) the issuing country of the credit or debit card that you use in the App Store.
Not all of them have to match, but the threshold is high enough that you're very unlikely to meet it while physically in the US.
Feature flags stay activated for 30 days since last eligibility, so if you're an EU resident and leave for a vacation, you're fine. If you traveled here as an US resident, you (probably) could get these features activated, perhaps needing an european Apple ID and/or SIM, but they would only stay on for 30 days.