Why are there separate categories for American English and British English? What if I have a question about grammar that is the same for both dialects? What if I want to know the answer for both dialects (if there are differences)? Should I post the same question in both categories?
Moreover, American English category has the whole … ONE discussion in it. Is it worth it?
I live in America but I still use the other English sections (and courses) since there’s more in that category. It’s probably best to do what you want.
Memrise recently split English into America and British, and it split Spanish into Spain and Mexico/Latin America. I believe that most English courses and discussions were automatically put in the British category, and Spanish in the Spain category. Bit by bit, courses are being moved to the correct category, and as new discussions are started, the American English (and Mexican Spanish) forums will get more posts.
Besides the fact that one of them allows an extraordinary number of spelling errors (originally in the name of cheaper printing) … 
Given the large differences in spoken word and also the different character sets used, I am still at a loss to understand why Cantonese hasn’t been recognised as a standalone category from Mandarin. An English person speaking the Queens English and an American from most parts of the USA will have little problem understanding one another generally (I intentionally omitted the likes of Cockneys and Scots ). It is said that a conversation between a Mandarin speaker and a Cantonese speaker is akin to a chicken talking to a duck (probably similar to a Cockney and a Scot having a wee natter aboot trouble 'n strife).
It’s not about the number of discussion. It’s about in what category to start a discussion at the first place. I believe, most discussion will concern both dialects, because they have much more in common than differences. That is why I see it as counterproductive to separate them.