Wiktionary
n. 1 The practice of actively preserving a culture to the exclusion of external influences. 2 The creation of a monoculture.
Wikipedia
Monoculturalism is the practice of actively preserving a national culture via the exclusion of external influences. Japan, China, South Korea, and North Korea are examples of monoculturalism. Usually a monocultural society exists by racial homogeneity, nationalistic tendencies, geographic isolation, or political isolation (sometimes but not always under a totalitarian regime).
Recently, right-wing governments in several European states, notably the Netherlands and Denmark, have reversed the national policy and returned to an official monoculturalism. A similar reversal is the subject of debate in the United Kingdom and others, due to evidence of incipient segregation and anxieties over homegrown terrorism.
Several heads-of-government have expressed doubts about the success of multicultural policies: British Prime Minister David Cameron, German Chancellor Angela Merkel, former Australian Prime Minister John Howard, former Spanish Prime Minister José María Aznar, and former French President Nicolas Sarkozy have voiced concerns about the effectiveness of their multicultural policies for integrating immigrants.
Nazi Germany practiced monoculturalism as part of its campaign for Pan-Germanism and German nationalism, but monoculturalism was typical of the era and many European countries were monocultural at that time. Some European countries are still effectively monocultural because of he people's shared culture and ethnicity, like Finland.