I've been to all those places multiple times. Love Lisbon and Barcelona especially. The Pena Palace is literally over the top.
Except Brussels, though. I've driven through Belgium a couple of times, and stopped for lunch at one town that had a thriving and diverse community of North Africans. Of course, I don't have your perspective and experience.
Heartily endorse researching views in travel destinations before spending a lot of money to visit and feeling uncomfortable and unwelcome.
I think that all over the world the modern conveniences of travel and communications are changing attitudes. It is one thing to be proud of one's heritage and culture, but if immigrants display the same values, they are unwelcome. Huh?
"Australia, Love it or Leave it" is a slogan I see sometimes on t-shirts or bumper stickers, and it is a dog whistle. Learn English, eat corned beef and meat pies, grow white skin, or nick off.
That's not a recipe for happiness. If I see someone from an unfamiliar culture, that is a learning experience for me, and a chance to be a decent human being and not a jerk.
Australia has had to accept migrant populations, and I think we are by far the better for it. For one thing, our boring British cuisine has come alive. It is a rare Australian family that cannot use chopsticks, or does not appreciate doner kebab. I have a wok and use it frequently. Hard to go past a good chicken and vege stir fry with black bean Szechuan seasoning and hand-pulled noodles.
There are few more uplifting sights than newly naturalised Australians, leaving a citizenship ceremony with their certificate and sprig of golden wattle, and they are the proudest and happiest people on earth. The sight of those happy smiles uplifts me.
But there are always a few dinosaurs around. The sort of men who think women should stay in the kitchen and cook boring food.