Nothing inherently wrong with it, except it is far to long for a cover letter.
The grammar and the English are fine. Had it been two maybe three paragraphs long it would be pretty much perfect. Remember that employers can get a lot of responses to an advert and, I will be brutally honest with you here, I probably wouldn't even bother reading all of that. Keep it short and to the point.

Let's not mix the issue with the race problems that Chinese schools have (I fully ack. these and it is a whole other subject). The quality of MOST of the letters, from native speakers as well as others, is what I was talking about.

Good luck to you Jack!