As the community matured, developers created small executable patchers (e.g., IW_Language_Changer.exe ). These tools did the file renaming and registry locking automatically. Some even extracted the English files from the game’s own base archives (which were often present but hidden) using a trick: the game shipped with all languages for debugging, but a flag in the executable suppressed them. The patcher simply toggled the flag.
Modifying files can sometimes trigger Steam errors or require a re-verification of game files. Call Of Duty Infinite Warfare English Language Patch