The PAL version definitely exists, but I can't find any evidence of the US release beyond mockups like on Gamerankings and entries in all these online databases. I just want someone to show me a picture of it sitting on a table to prove it doesn't just exist as an artwork asset
Please be aware that some of our database was imported from the old site, and some of the sources being used weren't properly vetted, so we may have some bad information. We try to clean up what we can when it's reported.
I'm not aware of Kao the Kangaroo 2 existing for Xbox.
It seems like it reached production, as it was assigned a UPC (742725272200), but was never released for NTSC. This tends to happen for a few titles per platform, and sometimes the pre-production copies slip through, creating extremely rare copies (NBA Elite 13 for PS3, for instance). I don't see a released ROM, however, which means that it's unlikely that someone at this point owns a copy, or the ones that are owned are sealed or owned by private collectors.
EDIT: The two people that "own" it don't actually own it. They're known to use the collection tool for their own tracking methods, which causes over-representation.