There is no American English vs British English.
British people speak a more proper version of English but even there English is not entirely proper.
That is the entire point of the entire conversation, NOBODY speaks proper English.
Therefore NOBODY should tell SOMEBODY else how to speak proper English.
Get it now?
What relevance does this have on a forum consisting of written words?
American English is a dialect of the English language, as is the Queen's English or Cockney or thickest Yorkshire.
But in the written medium, all these dialects share a single set of grammatical and (to a large extent) syntactic rules. So when I point out that your sentence "I don't live in California; should I prove you wrong again?" requires the semicolon, I am within the bounds of both technical and social correctness. You have already indicated an unwillingness to listen, so if this were not an open medium, one might argue that the post was wasted.
I write in praise of grammar Nazis. Imo the only people who dislike them are the ones who are at great risk of being told [how] to do it right. <sarcasm> My nose bleeds for them ... both barrels. </sarc> GNs perform a service not unlike that of an immune system ... usually unpleasant; almost always beneficial.
ceterum censeo The suggestion that a Big Mac can be classed a drug reveals an unfamiliarity with that grand instrument and institution: the dictionary, now oh so conveniently available online as Dictionary.com. If you read the definitions of the word, you will find that foods and nutrients are specifically excluded from the word's semantic umbrella.
So to your question "what right do I have to [correct your written English]?" I will say: the moment you commit a post to the public forum, you assume the responsibility for its correctness - both in form and in substance. As one whom you want to read your posts (implicit in the post's public nature) you automatically grant the privilege. We can bandy right v. privilege about ... but "let's not, and say we did". cn