Firefox spellchecker question

[ratcreature]

When Firefox spellchecks my input, the default seems to be set to Australian English for some reason. I would like to set it to American spelling as default, but I can't find such an option. It remembers when I previously selected US spelling for an URL (e.g. for the DW update page), but for each new one, it goes back to Australia.

I looked into the package list whether maybe I could just de-install the Australian and other unneeded English localization packages, but as far as I can tell selecting English automatically selects many countries, and you can't disable some localizations on their own. Similarly when I installed German, it now also offers me Austrian, Swiss and Luxembourgian spellchecks.