Why might two different countries have different structures of government?

The history of a country has a lot to do with it, the country's that went through the industrial revolution have turned out to be those where their prosperity has flowed on to the people in general. however these same countries as a result of their power have put the rest of the world in a state of turmoil that still exists today the USA for instance is constantly engaged in propping up dictatorships for trade and military logistics reasons.