Well I dug out a Windows machine and tried to get what you wanted, to no avail. As far as I know there is no UTF8 collation, it is an encoding. What you want if I am following, is the en_US locale (or equivalent for another language) on Windows. Anything I tried resolved back to a Windows code page. So the answer from my tests, is no you cannot match en_US on Windows.
Thanks for taking time out and looking into it !
Yes all the scenarios we tested didn't work for any of the utf8 code pages specified on MSDN or may be I don't know the correct representation of "language_territory.code".