<P> In the nineteenth and twentieth century, there was a significant increase in the size and scale of government at the national level . This included the regulation of corporations and the development of the welfare state . </P> <P> In political science, it has long been a goal to create a typology or taxonomy of polities, as typologies of political systems are not obvious . It is especially important in the political science fields of comparative politics and international relations . Like all categories discerned within forms of government, the boundaries of government classifications are either fluid or ill - defined . </P> <P> Superficially, all governments have an official or ideal form . The United States is a constitutional republic, while the former Soviet Union was a socialist republic . However self - identification is not objective, and as Kopstein and Lichbach argue, defining regimes can be tricky . For example, elections are a defining characteristic of an electoral democracy, but in practice elections in the former Soviet Union were not "free and fair" and took place in a one - party state . Voltaire argued that "the Holy Roman Empire is neither Holy, nor Roman, nor an Empire". Many governments that officially call themselves a "democratic republic" are not democratic, nor a republic; they are usually a dictatorship de facto . Communist dictatorships have been especially prone to use this term . For example, the official name of North Vietnam was "The Democratic Republic of Vietnam". China uses a variant, "The People's Republic of China". Thus in many practical classifications it would not be considered democratic . </P> <P> Identifying a form of government is also difficult because many political systems originate as socio - economic movements and are then carried into governments by parties naming themselves after those movements; all with competing political - ideologies . Experience with those movements in power, and the strong ties they may have to particular forms of government, can cause them to be considered as forms of government in themselves . </P>

What type of government structure does the us have