If you try to install Flash on Windows, by default Chrome gets installed too (and probably prompts you to make it default). It doesn't even ask you at install time, it's a default checked checkbox on the webpage you download from - very easy to miss.
I don't think it's regional. I'm in Sweden and if I visit the Flash install page with IE I get Chrome as pre-selected and if I visit with Firefox I get the McAfee add-on. (And when I'm using Linux, as usual, there are no extra applications installed.)