Why are most South American countries descended from Spain and Italy?

19, in the 20th century, a large number of Italians immigrated to the American continent, with the United States as the largest. There are also some immigrants to South America. After all, they all belong to Latin families and are all Catholic countries. At that time, Italians moved to South America mainly to Brazil and Argentina, where the population was mostly white, the economy was relatively developed and the politics was relatively stable among South American countries. But it is not accurate to say that "most South American countries are descended from Spain and Italy". It should be said that most of the whites in South America are of Spanish and Portuguese descent, and some are of Italian descent. Moreover, there are a large number of mixed-race whites and Indians in South America, as well as some pure-bred Indians.