Cultural/national identity: you are what you feel to be, imo.
I the op says "I'm English" why says "no, you're not" because of your ancestors or whatever.
I am half Italian, half German, so I always thought. Later in life I discovered that I actually have no Italian blood in me! I have now lived in Scotland more years than Italy and Germany both.
For many years I had a Greek Cypriot partner, assimilated his culture, a lot of people ended up thinking I was from Cyprus!
Whichever country I find myself in, they always say I'm too "Italian, German, Scottish" for some reason or other

Does not bother me, not even the "what part of Poland are you from?" or the "bet you make a good lasagna" (I do! but I like moussaka better!) not even the drunken " you took our jobs" (why haven't got any colleagues then?) or better "united nations, serve me first"

There is stupid people in any country, they have not kept up with the increasing inter cultural changes worldwide, my parents had it really bad in the '60s because they married outside their country of origin, that led to one of them always being unhappy when living in the other's country.
I think here in the uk more than racism there is a feeling of annoyance of other cultures customs, but sometimes the "other cultures" are a bit at it, like when I was working in asda at the fish counter a young Asian lad asked if the fish was "Halal". Even his mother laughed at this, told me there is no such thing.
Some of my English friends here in Glasgow tell me they feel discriminated, but others say it's nonsense, never happened to them.
But, as BOAB asks, why was the op told to efoff for speaking Portoguese?
A question on the by: why are all the official government forms in pakistani, urdu, polish, swahili

what not, but never Italian, German, French, Spanish?