A strange application-related situation Apple Support it's happening.
The app lists all devices linked to your Apple ID and allows you to receive assistance directly through the app. In addition, you can check your warranty coverage for one year (or longer if you have AppleCare) for your enabled products.
We don't know for sure when it started but, from time to time, when the language of the iPhone / iPad / iPod touch is set to “Portuguese (Brazil)” in the device settings (most users here in Brazil use it like this, for reasons), it is not possible to make an appointment at an Apple store in the United States or in any country other than Brazil. And there's no point in going to the Apple Support app and trying to change the location in your settings (by going to Change Location Account) because “Brazil” is the only option that appears.
Even if you are traveling in the USA or some other country that has Apple stores available, you will not be able to take advantage of the trip to book an appointment time and solve any problems you are facing.
How to work around the problem
To solve, relatively simple: change the language of the device (in General Settings Language and Region iPhone Language) to “English” and reopen the Apple Support app to change the location. In doing so, it is not only the US but all other available countries will appear on the list.
Intentional or bug?
After some tests with multiple languages, it was proven that the language of the device setting directly interferes with the list of countries available in the Apple Support application. If you distinguish Spanish as the language of the iPhone, only a few countries that speak the language (besides the USA, which has large Latin communities in some states) will appear as available to schedule a time; if you select the French language, the same thing happens.
In our opinion, if Apple really wants to limit access to scheduling, it would make a lot more sense for that feature to be related to your location (by GPS, the iPhone knows exactly where you are) than to the language used in the iGadget in itself. We have no way of saying whether such behavior is intentional or a bug, but we will hope that Apple changes that and makes scheduling schedules in its stores around the world easier again.