That is not defence, that is actually collectivism and authoritarianism without respecting human rights, equal treatment and freedom. What nationalist do is to use myths and identity politics around those issues in order to promote fear and collectivism, and corruption as well. Even on basis of racism and culturism. So they are not defending anything expect of their own strange fictions. Because things as culture and identity are based on social constructions and affections, which are changing all the time. The way you are presenting culture here is something else than what science and research has concluded many years ago.
Iceland is one of the most globalized countries and has quite open borders and immigration, even if the immigration levels are small because the country itself i small. This is why for example 3 million people from Africa cannot come to Japan because there will simply not be enough place.
Hungary and Poland have regimes with nationalist sentiments which are conducting corruption and statism. This is the especially in Hungary where the government is quite corrupted. government's policies there that are keeping many wages low and workers have problems to negotiate wages with their employers because the Hungarian government is a state-capitalist one. So the Hungarian government is not "defending" their country, they are defending their own positions. If you like corruption and cronyism, be my guest. Also, nationalism in Europe is historically and politically dangerous because it goes against ideas of European constitutionalism, democracy and citizenship.
Yes, I favor open borders and global free movement on basis of liberal/libertarian ideas. As with the case of Bryan Caplan, who for example shows that immigration from the developing countries does not lead to developed countries becoming worse. That is the point of libertarianism, that one does not care about culture, race or gender. One does not see people as being "imported" or "exported". One supports freedom for all humans simply because we are human beings with our freedoms, rights and sovereignty.
Also, those who are or who are seen as globalists also have their identification and affiliations with cities, states, regions etc.
Meaningless babel and again you didn't answer the question. These libertarian ideas will all die out if you import millions of foreigners. Just look at some stats on how non whites vote in the west. Why do 90% of blacks vote for the democrats in the US? is that a 'social construct'. Also Rights are only granted and secured by the state that you live in and they grew out of what would today be regarded as nationalist countries. They aren't made of sherbet and pixie dust , they have to be enforced.
Your English is really poor and its difficult to workout what your trying to say, but race and culture are not "social constructs" they are objective truths, you are completely lost in a world political correctness and lies. Here is a paper about racial differences. https://www1.udel.edu/educ/gottfredson/30years/Rushton-Jensen30years.pdf
Here are the voting stats
http://www.pewresearch.org/fact-tank/2018/11/08/the-2018-midterm-vote-divisions-by-race-gender-education/
This is my last reply, I'm not wasting anymore time. I cant argue with someone who thinks evolution stops at the neck and that cultures fall from the sky and lucky people get the good ones. I think unfortunately you have inherited your national average IQ of 89 or even lower. https://brainstats.com/average-iq-in-serbia.html