What is the language of my SQL Server setup files?
Within the root directory / folder of the install media, there should be several sub-directories/folders, including: x64, redist, resources, etc. One of those sub-directories will have a name starting with a 4-digit number and then 3 letters, possibly followed by another short group of letters:

####_AAA[_AA?]


That first group of 4-digits is the LCID, and the 3 letters are the language code. My installs for several versions now all have the following folder:

1033_ENU_LP

While the LCID is highly specific with regards to which language, the ENU portion at least matches the first pop-up you posted in the question that mentions:


  ... ENU localized files.


If you want to know what the LCID translates to, please see the following list on MSDN: Locale IDs Assigned by Microsoft. The number in the directory / folder name will match something in the far-right column: LCID Dec. For example, 1033 indicates a locale of: "English - United States".