This "localization" also includes the code for online payment methods available in a particular locale.

So for the traveler, when they arrive in a new area that's supported by Uber, the app will just work instead of a "Please wait while we download the necessary payment SDK for your current location..." notification.

You didn't just download Uber "for USA" - you've downloaded Uber for "all countries where Uber exists" just in case you might leave your home area and travel a location that Uber operates.

Testing matrix must be complex...