One of my repeated themes is that we join a new people when we follow Jesus. The old man is dead, our new identity is now the more important. I don't think our old identity has to go away. The NT writers sometimes delight in listing the many nations present and included, so it's not like being a Romanian, or American, or a New Hampshireman is necessarily erased. But it is often a treasure to us like any other, and thus provides a temptation. There are other identities of profession, family, or experience, and I think the same applies to those equally, though it's not my focus here.
As might be expected there is a verse to an old hymn about it.
Elect from every nation, yet one o'er all the earth.
Her charter of salvation: One Lord, one faith, one birth.
One holy name she blesses, partakes one holy food,
And to one hope she presses, with every grace endued