Earlier quoted context omitted.
Judging by the number of players imported from Latin America, I think the US only has enough players for a half-dozen MLB-level teams.
As I said in a cousin comment, the nationality of the players is irrelevant. I would count non-Japanese citizens playing in the NPB as members of Japanese professional baseball, just as I count Mo as a member of the MLB.
Comparing the two leagues, MLB has placed a greater emphasis on the home run (probably because Japanese players are smaller on average than many U.S. and Latin American players). However, that does not necessarily make the Japanese style worse when it comes to winning games. The World Baseball Classic is the only serious competition we've had to compare national styles at the highest level, and so far the Japanese system has won out. Granted, a sample size of two is probably not significant, but it seems all we have to go by.