A short plugging of the American Conservative University Podcast, first, which is a fountain of knowledge. It is rarely “fair”, as “both sides of the argument” are not considered on much of the excerpts that the podcast publishes, but if you have an interest in truth and justice (and parenting. I am 24 and I’ve got a number of years before raising children, but I have listened to probably ten hours of parenting tips over the past few months just because they are so radical and intriguing), you should listen to the podcast.
Anyway, cultural isolationism in all forms is harmful to a people, a society, and ultimately all of civilisation. All cultures nowadays are amalgamations of a traditional essence of a people (of which there are many forms) and a massive number of borrowed traits. Most of the time these traits can be mixed up and switched out depending on their effectiveness. For example, if an immigrant to another country can swallow his pride enough to learn the language and culturally appropriate the mannerisms of that country, while also keeping his own culture in his heart, he is more likely to succeed in that new home (look at the Jews, the Chinese or the Lebanese). This is not to say that one culture in essence is better than another, just that there are more preferable and less preferable traits within those cultures, an understanding which is ignored or intentionally suppressed in modern society.
The data is out there—for anyone interested, please read Wealth, Poverty and Politics: An International Perspective by Thomas Sowell—but I will give just one obvious example of cultural isolation: Spain translates more books into Spanish in one year than the sum of all the Arabic nations have translated books into Arabic in the last thousand years. This wide dispersion of culture teaches tolerance within western society over the past two hundred years has brought overwhelming equality, respect and insurmountable progress, things which a number of Arabic nations do not have, and even vehemently oppose. Nowhere is this clearer than in America, where positive cultural traits were adopted by all and negative traits were forgotten, in the Melting Pot, that experiment which has led to human prosperity, well-being and freedom the like of which no one on the Earth ever thought possible just one hundred years ago. The trick, which America (and all of humanity) is still learning, is how to know which cultural traits are good and which cultural traits are bad. The fact that there are drawbacks with this system (lost culture, diffusive minorities) does not always mean there is a better option.