By coming from different country their native language (IE what language they heard as infants) more closely resembles that country than America. Note I said 47 million and there are more than 47 million immigrants.
There are also some native born Americans to immigrants who also don’t have English as their first language and People born in China whose first language is English, but that’s ever smaller refinements on a specific estimate.
> ~47 million Americans aren’t native English speakers having immigrated from a non English speaking country.
Your link says 46M total which includes native speakers. So it does not state how many non-native speakers. (not that it would matter as most would be proficient english speakers, just pointing out you're exagerating and your numbers are wrong)
The question of your native language is answered long before any of what you’re talking about here. A 20 year old isn’t time traveling to have different parents when they take an exam.
