One persistent issue with the Ubuntu installation process is that it always seems to decide that Michigan is in Canada. Whatever the reason it does this, the solution has always been fairly simple: go into settings and make sure all of the locale/language settings are set to U.S. / English. Linux Mint 13, being based on most of the same packages as Ubuntu, has the same issue. However, settings alone wasn't doing the trick after migrating from Ubuntu 12.04.

Every time I logged in, a dialog would pop up indicating that en_CA was not installed (which it wasn't) and that it would revert to the system default. In the terminal, the locale command was correctly showing en_US but a little poking around found that my home directory contained a .dmrc file which was attempting to override the language / locale. After removing this file, the account now uses the values from the system defaults.