OP, your husband made a racist comment, and when you attempted to explain why it was racist, he didn't learn from it. He simply decided not to say it out loud again for an easy life.
You live in a predominantly white area, so there haven't been many opportunities for your husband to sprout some casual racism. Doesn't mean he wouldn't have, had there been other people of colour move to your area sooner.
You cannot say your husband is not a racist unless he learns from his ignorance and changes his worldview. Shutting up for a quiet life is not being anti-racist. It's hiding your true self.
The question was horrible. And some of the responses on this post have been horrible.
There is absolutely something wrong with asking someone 'no, where are you originally from?' or 'where are you really from?' This line of questioning is very different to 'what is your ethnicity?' as it doesn't show curiosity, it shows rejection of that person and their right to be there.
It can also be a complicated question with lots of baggage and it's not something that necessarily feels right to bring up on a first encounter.
I tell people my story when I am comfortable with them and it feels natural. I don't tell strangers. If we click, I might tell you immediately. It might take me 5 years. I might never tell you. But you can ask me where I live now. Anything beyond that feels intrusive, especially if you reject my answer and you want a different answer.
Anyone who doesn't understand that is showing their privilege.