Indeed Shamo may have come to meaning 'fighting' in Japan. However, there are lots of other sources that say the term 'Shamo' is a corruption of the word 'Siam.' I believe the latter as know one denies the fact that these birds are nothing more or less than Thais that were bred to a slightly different standard and taste.
If you will look at the birds on the map you post (found on page 76 of my good friend's Horst Schmudde's book) and the Keeling type birds, even the untrained eye should notice a marked difference in the two!
Those birds are much more like the Earl Ashby strain of Shamo that ended up on Manuel Reynolds' yard! Why because a heavy weight boxer does not stand straight up to box! He bends slightly forward.
I'm not saying the Keeling birds aren't impressive; they most certainly are. I'm just saying the old type, imo, represents what was used in Japan and in America: common sense dictates it.
As to the mixing in America; certainly it happened. However, there are still men alive who saw those original birds and who kept them. They will tell you what those first birds looked like..... and it wasn't like the Keeling birds. As a matter of fact, one of those men from VA after seeing the Keeling birds and getting use to them no longer even calls the MR birds 'Shamo' because they are so different. That is where I differ completely with him.