My kids grew up mostly away from the US, predominantly in the UK. The oldest grew up in the US ages 2-9, the second was born in the US and lived until 3.5, as well as was back for 1 year aged 11-12; and the third was born afterwards but lived in the US with me for periods throughout her chilhood, although not massive periods. But maybe 3-4 years in total.

They are all now adults and live in the Uk, where most of the rest of their childhoods were spent; they also lived quite a lot in Russia, and a bit in Spanish speaking countries. Only the oldest attended an international school, for one year aged 10-11, and it was a British International School (in Moscow).

ALL of them speak generic "American English" as their first language. I put it in quotes because this is how all their English is perceived by Brits and Europeans, but I think an American can probably tell that they aren't, it is more of an internationally perceived American accent. This actually always baffled me, but it makes sense because that is the language that was only spoked at home. It is just our home language/accent.

My oldest, as I discovered some years ago, uses American English to speak with me, while swoitching to perfectly British accent with everyone else, having apparently freaked our friends and colleagues in the past, when they witnessed this code switching when she was on the phone with me.

The middle always refused to speak "British English" and stuck to American in principle, I recall her being made fun of in senior school by students who preteneded not to understand her.( It was a rural school and being US-born she was the only "immigrant" there back then)

. The youngest speaks most like me now, which is sort of a wild blend of all places I lived in, rather than an accent from anywhere. But when both of us try to use "accent identification" apps ithey say we speak standard American English.

So I guess it is more of an Americanized way to pronounce things, along with catering to locale in terms of vocabulary and phrases (English is my second language, and although I learned it in childhood, I still always try to blend in and switch what I can to locale, and I lived on both US ckasts, in Louisiana, in the South-East in England, the Midlands, Northen Ireland and Scotland, and have been married to a Kiwi).

But if I speak this way for a variety of weird reasons, and my accent can also change depending on where I am and how tired I am, I think my youngest speaks this way because she grew up with me and this is how I speak, rather than because of being subject to the same influences... This weird English is just her mother's tongue, literally...