Europe and North America have long diverged in their immigration policy. Simply put, Europe was from the early 1800s until the 1950s a continent of emigration, whereas the United States and to a lesser degree Canada were quintessential countries of immigration. Canada and the United States encouraged Northern European immigration with the goal of building white, Anglo-Saxon settler societies; Europe encouraged emigration with the goal of exporting surplus population and unemployment (Germany, Italy) and/or empire building (the United Kingdom). In the postwar years, divergence continued. The United States and Canada abandoned the race-based, exclusionary inflection of their immigration policies, and opened their doors to an extraordinary migration from East and South Asia, the West Indies, Latin America, and Africa. European nation-states tried to have their cake and eat it too: They tried to harness the economic benefits of mass unskilled labor while ensuring that the migration was temporary. These efforts largely failed: The liberal constitutional order that is common to Europe and North America meant that the immigrants were not simply workers but rights-bearers, and European courts frustrated national efforts to guarantee the migrants' return.
The result, by the 1990s, was a demographic makeup that looked broadly similar on both sides of the Atlantic. European and North American societies were multi-ethnic; the bulk of migrants and ethnic minorities lived in their cities; and (with Canada partially excepted) the migration patterns were dominated by family reunification.