Google App Developer: Change Default Language of App

click "add translation", select US English.

This shows another button "manage translations", and you can change the default language, or delete other translations.

Go to Google Play Console > Store presence > Store listing.

Click Manage translations button, then Add your own translation text and select English (United States) - EN-US from the list.

Once you have two different languages set for your app, click again on Manage translations and choose Select default language, going for the right one this time.

If you want to remove the previous language, select Manage translations and then Remove translations.