Worldwide this is the case too, the NPB doesn't want to participate either and only does because their players are nationalistic enough to want to anyway.
Not true, they've wrapped the Japanese baseball flag around "Samurai Japan", call all their youth teams Samurai Japan, they hosted the international baseball federation's Premier 12 event as a competitor to this event to showcase Samurai Japan domestically (the Japanese lost in the semifinals leading to a USA-South Korea final, and the event suddenly lost its TV coverage in Japan), they've invented teams for Samurai Japan to play against (had a 2 or 3-game exhibition series once vs. Team Europe).
NPB are "against the event" because they want a larger share of revenue. They're heavily for Samurai Japan however.
If they're serious about growing the game they should. It's arguable that baseball has a bigger international appeal than any of the big four sports in the U.S. (probably basketball has more, but you know the U.S. will win every tournament no questions asked, that's not true in baseball).
My opinion of the way forward is to think less tournament and more 5 or 7-game sets between two nations, "tours" a la rugby union and cricket.
Think about this for Novembers where player eligibility is analogous to the IIHF Worlds.
Puerto Rico vs. Dominican Republic
- 2 games in San Juan
- 2 games in Santo Domingo
- 3 games in Miami
USA hosting against anyone of a decent enough level can easily find a couple sites to host a series between them and one of the larger baseball countries. Mexico aren't that good compared to the U.S. but they'd sell a lot of tickets vs. the U.S. for a venue in Texas, Arizona, or Southern California, which is 6 MLB stadiums combined. It's not like a baseball team owner whose team did not make the playoffs would turn down someone using his stadium.
Canada could host at the Skydome and the Olympic Stadium if they so desire. The Caribbean countries with the exception of Cuba could host a game or two but finish in the U.S. as a cash grab. The East Asian countries of Japan, South Korea, and Taiwan are the oddballs as they can come over to play but to be fair you'd have to negotiate to go over there, leading to likely weaker lineups going on the road.