Here’s what being non-natively bilingual means.
It means that I didn’t grow up speaking French, but I speak it now.
It means I’m proficient, not fluent. It means I speak French well enough that a surprisingly high number of people have been mislead into the assumption that I’m actually French, but I still sometimes have to ask French people about vocabulary words.
It means that I can write pretty darn well in French, but if it’s a professional thing, I’ll have a native French speaker edit it.
It means I can slip very easily between French and English. It means I can slip very easily between the US and France and England and Madagascar.
It also means that my brain is wired one way, with additional circuits that have been added as the years have gone by.
When I’m in a French-speaking environment, I think in French. (That was one of the ways that I knew I was finally becoming comfortable with the language, when I could think and dream in it.)
When I’m in an Anglophone environment, my brain reverts to its original programming. And it reverts so much that all my memories transform into English memories. Any recalled speech from a French conversation is automatically recalled in English, and if I were to want to recount the actual French words for someone, I’d have to retranslate it back to my second language in my head.
Brain circuitry is weird. I don’t quite understand it sometimes.