You could have just asked, but I don't think it's particularly important information.

I don't actually care, I just wanted to point it out to you, so that you understand how strongly it's colouring your views. We all have our biases, and we should all be aware of them.

How strongly is it coloring my views of what somebody else presumably from the same country said?

The fact that you presume him to also be American is another super American trait.

The person talked in depth about things happening in California. I can't be certain they are American, but I have ample reason to presume they are.

And you hail from some magical fairy land with no history of oppressing others, so it's clearly fine to make light of Irish oppression. Only an American would find that action racist.