Firefox: language packs / en_GB dictionary

Is it expected to have Firefox install support for dozens of languages? Every time there's a FF update, I see a long delay and a dialog poops up showing many language plugins are installed.

Also, somewhere along the line, FF has switched to the en_GB dictionary/spelling check (based on which words it's marking). I have no idea how that happened or how to get back to en_US.

$ locale LANG=en_US.UTF-8 LC_CTYPE="en_US.UTF-8" LC_NUMERIC="en_US.UTF-8" LC_TIME="en_US.UTF-8" LC_COLLATE="en_US.UTF-8" LC_MONETARY="en_US.UTF-8" LC_MESSAGES="en_US.UTF-8" LC_PAPER="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" LC_IDENTIFICATION="en_US.UTF-8" LC_ALL=

Thanks for any ideas.

<Joe