While I am not based in America, I am originally from there, which is reflected in the way I write. I am capable of writing in both British and American English, and can very easily transition between the two.
English is my native language, and it goes without saying that I have no issues with grammar or spelling. In fact, I am more than willing to help improve a piece of text if needed, although I am happy to simply proofread.
I believe that both my proficiency in English and the efficiency of my work will prove themselves to you if I am given this work opportunity.
Eric.