Hello TheParser. Sorry for the intrusion but I feel concerned.
English is a language at first, so the main purpose is to be understood. Accordingly, as long as you are understood, who cares? BrE is considered, as far as I am concerned in France, as the standard English. However, I would never say it is improper to speak AmE. I want it that way, folk.
You must certainly be stumbled upon people who do not know much of English