You need to read up on the history of the Irish in the UK and how they were treated by the English very much as a distinct race, and one that they thought it was very much OK to abuse.

Here's a quote from the Rev. Charles Kingsley, a Victorian theologian and defender of Darwinism;

I am haunted by the human chimpanzees I saw [in Ireland] . . . I don't believe they are our fault. . . . But to see white chimpanzees is dreadful; if they were black, one would not feel it so much. . . ."

Literally describing Irish people as subhuman. This attitude was wildly popular in England. Even in the eighties and nineties it was still common for occupation troops in Northern Ireland to refer to the Irish as "white n****rs". This attitude, that the Irish are subhuman, justified horrific acts of racial violence that happened in my lifetime, and probably yours.

The Irish have been the targets of military occupation, police abuse, disenfranchisement and genocide, all on the basis of what the English very much considered to be their "race."

Again, America is not the world. There are whole layers of complex interactions of identity happening out there beyond your borders.