re: Would the WBC be more interesting if the United States played by state instead

Regardless of the referendum, Puerto Rico is unlikely to become a state any time soon. Because the island remains a territory, the decision is ultimately out of boricuas’ hands. Only the federal Congress, to which the island appoints a non-voting “resident commissioner”, can grant statehood, which it has not done since it admitted Hawaii in 1959. Until the most recent referendum, Puerto Ricans had never voted in favour of statehood, so Congress had no reason to act. That obstacle has now been removed, but coming on the heels of a government shutdown and a brush with debt default, the legislature is highly unlikely to prioritise a Puerto Rican statehood bill.