Can someone with no ethnic connections to a nation ever truly belong to that nation?

[TEUTORIGOS]

Yes, because multicutural countries like USA, Canada and Brazil exists

Canada is British and French (yes, there are minorities though) , Brazil is a third world shithole and America is not a country :

[Decius]

No for europe but yes for US & Canada

[TeutonicBoyars]

Answering this from a European perspective:

I'm confused by the question. Are you talking about "race" (the thing we understand as having some biological ground in which why people from different populations look different from one another) or "ethnicity" (that is, a cultural group).

While none of the following necessarily reflects my views, suffice to say, when it comes to race, a person of African or Asian origin will always look like an outsider in France or Germany and the natives would most certainly carry some prejudices (not necessarily ones meant to be offensive, mind you) towards them because they are identifiably different to the natives because they do not descend from the same ancient populations that we would consider "races".

When it comes to European groups then it's quite different IMO. If a person traces all his roots to Ireland I don't think he would ever be disqualified from belonging to England, Scotland, Wales, or even France, IMO. I don't think a Swede would ever not be able to become a full Norwegian (or, at the very least, his children would) or a Dutchman to become a German, an Austrian become a Czech, a Slovak become a Hungarian, a Spaniard to become a Portuguese, etc etc. These groups have been neighbors for thousands of years and have inevitably mixed, as it was even more easy to do so before there were political borders.

Just my take on it.

[Mikula]

It is individual

[Visage pâle]

Some individuals can assimilate, yes. Not when there are communities.

[Bogdan]

No. Assimilation does not gift you native blood. You could adopt another’s culture but you’re not them after that.

[Alexandro]

Never. A man born in a stable isn't a horse as well.

[Russki]

No.

[capocannoniere]

No. Even me as a 7th generation immigrant have a lot of cultural and mindset differences to the Brazilians of say, Rio de Janeiro. I go to the point of saying we are like a whole new province of Italy if we talk about culture. We have our own dialect, even our own food is still based in North Italian pillars such as Polenta, risotti, pasta like bigoli, tortelli, capeletti, our own wines, cheeses and the like. While these things are far from being as ubiquitous as they were before WWII repression, but it still exists and has no possibility of dying.

Italian-Brazilians will assimilate once and for all only the day where we dillute A LOT into the local portuguese/indigenous/black population. Many people with only partial Italian blood still adopt our mannerisms.