Should I learn to speak with an American or British accent?
People often ask me what variety of English they should learn. Here's my honest answer:
It doesn't matter.
Accents are hard to change.
It's really, really hard to pick up a native-sounding accent if you learn English as an adult. Children pick up accents very quickly, but adults don't. Even after speaking English every day for twenty or thirty years, you'll probably keep a bit of a foreign accent.
I've met many English learners who've lived abroad for several years in an English-speaking country. For the most part, I can't tell what country they've lived in unless they tell me.
Since it's so hard to learn an accent, you probably shouldn't spend a huge amount of time trying to guide yours to one version or the other. There are better ways to use your time, like learning new vocabulary or memorizing phrases.
English speakers are used to different accents.
Even if you are able to gain an American or British accent, it won't make much difference. That's because English speakers are used to hearing a variety of different accents. Americans hear British accents on TV and movies, and vice versa. And we all hear accents from other countries: Russian accents, Korean accents, French accents, and so on.
If your accent matches the people around you, you'll fit in with them. If it doesn't, people will think that you sound interesting and exotic. Generally, British people like the way that Americans sound, and Americans like the way that British people sound. So you're OK either way.
Go with what's easiest
Just pick whatever language is most convenient for you. If you like the PhraseMix method of teaching, you should probably learn American English. If you have British friends or coworkers, maybe it's better to learn British English.
It's probably easiest to stick with just one variety. However, there's nothing wrong with mixing a bit of British and American English together. It won't hurt you!