En_US Localization always selecting default 'en' and not 'en_US'

I'm trying to add Localizable strings to translate push notifications on the device side. This works fine when adding different languages (ex: German), however I'm running into issues when trying to add a Localizable file for en_US. The default is set to the en file.

I've tried setting my phone's language and region to en_US and US, as well as building my app and editing the scheme in XCode to use en_US as the locale but the notifications always get translated using the default en file, and not the en_US file. My goal is to have a separate notification translation for en_US vs for any other English locale but I'm stuck here.

Any ideas would be appreciated!

Something interesting to note: When I add a debug print statement in the app itself with one of my localized strings it correctly selects the en_US variant, however the notification selects the base en variant.

En_US Localization always selecting default 'en' and not 'en_US'
 
 
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