Can the keyboard menu be removed/hidden after installation? I've tried a customized removal of several language options, a reinstallation of the keyboard control panel, etc. What to do? Thanks.

I think the Unicode keyboards (??) don't get removed once language kits are installed. An old workaround I used with multilingual language access in 8.6 is to boot with the option-space (this combination is buried in the Help somewhere) keys held down.

This makes the language files and keyboards appear in the system file, and you can drag them out just like sound files. Interestingly you have to remove the language files first, then you can move the keyboards otherwise the keyboards appear again.

Once you remove the Unicode keyboards, you should have no keyboard menu. (I haven't tried it on 9 but I can't imagine this to be different)

Yep, this is right - it took me some digging
in TILs to find this out... I removed the
Unicode and Extended Roman Keyboards but that
American flag kept showing up in my menu bar.
Apparently there's a script in the System
file that puts the Unicode keyboards back in.
Remove this script (called "Unicode") along
with the other keyboards in the menu and
it'll go away. The TIL is at
http://til.info.apple.com/techinfo.nsf/artnum/n24661