This phenomenal myth that the OH was more accepted in Europe is just a myth. Allow me to prove it that this is just not true.
A. The Chofetz Chaim was the recognized Gadol (see many stories that only when he was there it was decided). Also all of his letters in the KOl Kitvey always have him first the Rav Chaim Ozer then either the Lubavitcher Rebbe of the Gerrer Rebbe. Also see that Rav meir Shapiro and Rav Chaim Soliveitchik were machnia to him.
2. The OH quotes the MB 25 times, clearly you see that the MB was so popular that he made it to him. 3. If you look at the KOl Kisvey of the Chofetz Chaim you will find that almost every letter is asking for a set of his sefarim (which is quoted by many Rabonim of his time Achiezer and Shoel Mashiv and more) while if you look at the OH Kol Kisvey you will find a total of 2 maybe 3 letters asking for his sefarim (besides the fact that Orach Chaim was not printed until much later 1910).
If you compare the letters of the Chofetz Chaim to the OH you will see that the CC has correspondence with Rabonim all over the world while every letter of the OH are all addressed to Russia (besides one or two).
To conclude it is all a myth, the CC was the accepted leader of klal Yisrael and his Sefarim were also accepted as such (i’m not saying the OH were not u understand my point). Also Rav Henkin was a Talmid of the OH and Rav Moshe lived in russia so it is no surprise that they held this way while the rest of the world did not.