Set default language to English (US) in 12.04
Solution 1:
OK, I ended up doing this a different way.
First I googled around for the file where this setting is stored:
sudo nano /etc/default/locale
Then there were a bunch of '_CA' below that I changed to '_US' like so and everything worked.
LANG="en_US.UTF-8"
LANGUAGE="en_US:en"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
And then USA #1.
Solution 2:
Under Settings>Language Support just drag the greyed out English (United States) to the top, with plain English under that. This will activate the US locale. You may need to check the Regional settings tab as well.