The impression I get is that not only is the US mirrorless market smaller than that in Japan and the far east but its also got a very different makeup.
In the far east I'm guessing your looking at sales more akin to the DSLR market, lower end bodies make up most sales which become progressively less for higher end bodies. In the US on the other hand there just doesn't seem to be as much interest in lower end mirrorless releases(such as the J4 and EOS M), looking at amazon's sales chart I think its notable that higher end models are placed further up than on the DSLR list.
In this kind of market I can see the sense in releasing the V3 but not the J4, especially when you also have a strong market share for DSLR's and high end compacts.
To me, the slow to adopt process of both Canon and Nikon to a mirror-less full frame solution has been interesting to watch. Not sure why both companies feel that this market (mirror-less full frame or APS-C) is not a good place to be.
Canon is in the ASPC mirror less market of course but I think we've seen with the recent Sony FE system that FF mirror less isn't quite as plain sailing as many thought it would be. Lens balance and issues with light angles are significant problems that seem like there not going to be overcome easily.