All my scratch orgs gets created with the user-language set to Danish which is a good guess but I cannot find anything in Setup that way. No Dev Hub setting I’ve found can change that but setting the language in the scratch org definition file will. That’s easily done from the terminal with jq.
cat config/project-scratch-def.json | jq '. += {"language": "en_US"}' > config/project-scratch-def-en_US.json
lekkimworld.com 