Hi there, this is Marc. Thanks for reaching out to the community.
You don’t need a clean install to fix this. In Windows 11, go to Settings > Time & language > Language & region and make sure English is set as the Windows display language. Then remove Spanish under Preferred languages. Next, go to Settings > Time & language > Administrative language settings > Copy settings and check both boxes to apply English to the welcome screen and new user accounts.
To fully clear leftovers, also check Settings > Apps > Installed features and uninstall any Spanish language pack that still shows. Finally, restart your PC so the changes apply everywhere. This should remove the traces of the old language pack without reinstalling Windows.
Best regards,