Change the Windows regional settings (edit)

Configure International Settings in Windows | Microsoft Docs (HAY HAY HAY)

Get-WinSystemLocale

Set-WinSystemLocale ja-JP --- Japanese (Japan)

Set-WinSystemLocale en-US --- English (United States)

Restart-Computer

Change the Windows regional settings to modify the appearance of some data types - Access (microsoft.com)

The display language you select changes the default language used by Windows features like Settings and File Explorer.

1. Select Start  > Settings  > Time & Language > Language.

2. Choose a language from the Windows display language menu.

Use PowerShell

Get-WinSystemLocale

Set-WinSystemLocale ja-JP --- Japanese (Japan)

Set-WinSystemLocale en-US --- English (United States)

Restart-Computer

Get-WinSystemLocale (International) | Microsoft Docs

C# Change default language programmatically

locale - Change system default language programmatically with c# - Stack Overflow

Instantly Changing Language in the Form - CodeProject