The US gave the world a model.

The world looked at how the US handled immigration, melting pot etc, and decided to implement it so they can solve their worst issues

Unfortunately they did that without any deeper understanding of what made America great. Zero comprehension of the constitution, the mentality of the US citizens, their history. Freedom being central, decentralized safety through gun rights, freedom of speech rights, the process of naturalization…

So Europeans decided to open the gates wide and do the American thing without the prerequests. Without them doing their homework.