The Europeans, both leaders and regular citizens, failed to fully realize the cultural give-and-take necessary when they overlooked the Roma (Gypsies). Roma form the largest stateless minority in Europe. Many Roma are in the process or have already fully integrated into the popular culture of their respective nations but some continue to live the nomadic and sometimes beggar lifestyle. The latter group keeps itself seperate from mainstream European culture.
The end of border control within parts of the European Union has allowed many of the latter group to enter Western Europe. Europeans do not know what to do with the latter group. Some proposals are reasonable while others come straight out of the 1930s. Denmark sought to put Roma kids in special classes that focus on cultural integration but the move was declared illegal, Finland has threatened to take children away from Roma who make the kids beg, and Italy has fingerprint enforcement of Roma. With the Jews mostly gone, either killed during World War II or left for Israel, Europe is not handling its minority issue well.
The problem is that even progressive Europe cannot deal with a culture so foreign to it. Similar problems exist with radical Muslims who use Europe's freedom but do not share its classical liberal ideals.
The cultural conflict in an open society serves as a warning that culture must be dealt with even today. Those who propose other open border pacts like a North American Union can point to the economic benefits for all, but they also must realize that there will be so-far unsolved trouble when different cultural groups come into contact.