If your Steam account is region-locked (e.g., a Russian key that only allows Russian language), the dropdown menu will be greyed out. In that case, you must contact Steam Support or seek a manual pack.
“Do you want to uninstall? Y/N”
Some versions require you to manually edit localization.txt . Open it with Notepad. It should contain a single line like: english Or sometimes: english 1 If it says russian or polish , change it to english , save, and close. Call Of Duty Black Ops 2 Pc English Language Pack