Which of the following are the most numerous in North America?

States.

Expiation: When referring to the geographic delimitation of North American's countries, the matter isn't uniform. Some specialists in the matter state that North America spans three countries: Canada, the United States and Mexico. Others also include Central American's countries in the delimitation. And, even others only consider the U.S. and Canada as part of North America. The following answer is based on the first delimitation given.*
The most numerous in North America are the States, which in total are 89.
Number of States in North America: 89.
32 states in Mexico, 49 states in the United States (the U.S. has 50 states in total, however in North America are only 49 since Hawaii is geographically located in Oceania) and 10 provinces in Canada (Notice that Canada uses the term "Province" to describe its divisions).
Numbers of countries: 3
Canada, The United States and Mexico.
Numbers of Oceans: 3
North America is bounded by the Arctic Ocean, the Atlantic Ocean and the Pacific Ocean.
Number of Nations: 9
New England, The Foundry, Dixie, The Breadbasket, The Islands, Mexamerica, Ecotopia, Québec and The Empty Quarter.