Theme is looking for language that is not installed

[Holohugo]

Hello! PS 1.7.8.1, PHP 7.4

Im using Warehouse theme and i have problem with English translation files for it. Theme is looking for en_US, but i have in my shop installed en_GB. There was never en_US in my shop. This affect translation (i cant access EN translation from BO) and mail templates also. Is there a way how to force my theme to use en_GB? I tried to crawl files for any en_US string to change it manually, but it seems it doesnt have any. When i add en_US folder manually, translations are accessible again from BO, but none of the changes are visible in the shop, since that uses en_GB.

Any advice on this?

Thank you!