I very much enjoy this author. He and his brother wrote a book called "The King's English", in 1908, and revised it a couple of times. He treats Americanisms as a special class of foreign words, and is generally opposed to their use, mostly for the reasons he opposes the use of foreign words in general. He is, after all, writing about the
King's English. But he does defend Americanisms from unwarranted criticism, and points out that some Americanism are simply older British expressions. However, injecting them in British writing imposes a burden on an English reader unfamiliar with them.
Mark Twain could not be reached for comment.