What is the reason behind most anime being dubbed in American English and not British English? Does the control of a country over the world market have something to do with this?
Because most of the companies that first get the licenses to distribute a series outside Japan in English are based in America.
If we look at three of the biggest ones that I can think of off the top of my head, we have:
- Funimation - Headquarters: Flower Mound, Texas, United States
- Aniplex of America - Headquarters: Santa Monica, California, United States
- Crunchyroll - Headquarters: San Francisco, California, United States
When companies in Anglophone areas outside the U.S., like Manga Entertainment (UK), Madman Entertainment (Australia) and Siren Visual (Australia), get licenses to broadcast outside of America, it would be a waste of money to re-sub/dub the series. This is why when you get DVDs/Bluray from somewhere like Madman, you see company logo animations for all the companies involved, including U.S. companies like Funimation or Aniplex, before the title menu.
Re-subbing might be significantly cheaper since you are replacing words based on how they are spelled (color/colour, meter/metre) but re-dubbing wouldn't be because you have to hire the voice actors/actresses to come in and redo lines. If the original VA's were re-hired then it would be possible to get them to redo certain lines, but if you wanted a UK VA Cast then you would need to redo every scene and this wouldn't be cheap.
Also one thing to consider is that Japan does have different accents such as the case with Toji who has an Osaka accent which was interpreted to be a New York/Brooklyn accent. If an English-speaking company outside the US was to re-dub they run the risk of ruining this and we know how bitchy we can be when it comes to subs/dubs not being accurate.
I'm going to distill this comment to an answer.
It largely depends on what region the dub is intended for, and also who is paying for it. There are a lot of differences between the two English styles, and it's important to ensure that the market which the dub is intended for receives the correct-sounding audio.
I've personally noticed a trend with dubs in that America is its principal market. This doesn't exclude any other English-speaking countries, but given that America is one of the larger markets for dubs, it makes sense to go that route.
If a dub is not localized to British English, then either there is no budget to do so, or the differences in localizing the audio wouldn't be quite significant enough to justify the effort, and the American English version is "good enough".