The way a country determines its regions and methods of ruling them depends on what country you are talking of. Prefectures are the subdivisions in Japan, 43 main and 2 urban and 2 others. They don't have a separate constitution. They are governed by governors and assemblies.
The United States has fifty states, each having a degree of say in how it is governed with differences between state laws. Canada ten provinces and three territories. States are directly governed by elected senators in the US but the country is ruled by the budget which is determined by the government.
The US is unusual in allowing its president tremendous power, which is why a very careful examination of a candidate's morals, ideas, ideals, temperament and capability would be a good idea before an election is held.
The answer to this question depends on what kind of a “state” is being asked about. For example, states within a country like the United States (U.S.) are individual geographic regions. There are 50 states in the U.S. In Japan, there are 47 different individual geographic regions but they are called prefectures.
I believe the only other country in the world that uses the word prefecture is France. In Canada, the word province is used instead of the word state or prefecture. The word state can also be used when referring to a country. A country can also be called a nation-state. A little bit confusing, huh?