Let us not forget it was the treatment of newly arriving Italian immigrants by the Dutch, English, German and Irish immigrants who had arrived in previous decades, that promoted the rise of the Mafia in the US. Sadly, in this country one does not become American until you join in with previous immigrants to denigrate the most newly arrived immigrants, except in some cases those discriminated against were actually here before any immigrants, such as native Americans and Mexicans. In fact, at one point half of the US was actually named Mexico which Spain sold to Fance who sold it to the US in the Louisiana Purchase. Hmmmm, Spain sold half the US to France who sold it to the US, how the hell did that work? They have a few outposts in millions of square miles and claim it and all indigenous people within it as theirs, really how the fuck did that work?
And for the record, Native Americans were not defeated militarily, it was through treaties with the American Government, of which every single one was broken by the US, that enabled conquest of the American Indians. The American Constitution was inspired by the Iroquois Confederacy which is the oldest established democracy in the world and since there were no contemporary democracies in Europe, the Iroquois Confederacy became the inspiration for the founding fathers.
To single out Columbus as the perpetrator of the cultural changes that occurred as a result of the interaction between the Old World and the New World, is to ignore the movement of different cultures in the world previously, such as the conquest of Judea by the Egyptians and then Rome and the enslavement of the Jews. It is man's nature to have conflict and to conquer and enslave other men, this has been repeated over and over in the course of the world's history.
American Indians were in Europe, 500 years before Columbus arrived in Hispaniola and without their help, immigrants like the Pilgrims never would have endured the harsh conditions they encountered. The reward for their help was to be exposed to diseases they had no immunity to resulting in pandemics which make the current one look like a joke.
As Furio pointed out above, it is the part of hypocrisy of this country to discriminate against the newest arrived immigrants by the older immigrants, that's just the way it is. Who told you life was fair anyway?