Yeah it should ask for restart immediately.
If you can't get it to change with a restart now (just change it to English and click OK even if it doesn't ask for restart and restart yourself) then there are 2 things you could still try:
1. System restore / system file checker tool (google it)
2. Creating xml file with notepad
<gs:GlobalizationServices xmlns:gs="urn:longhornGlobalizationUnattend">
<gs:UserList>
<gs:User UserID="Current" CopySettingsToDefaultUserAcct="true" CopySettingsToSystemAcct="true"/>
</gs:UserList>
<!-- system locale --><gs:SystemLocale Name="en-US" />
</gs:GlobalizationServices>
and running in command prompt (admin mode) where D:\locale.xml is whatever the file path to your xml file is
control.exe intl.cpl,, /f:"D:\locale.xml"
and then restarting your PC.