“Most people” or “Natives?” It’s easier to fool people who don’t speak that dialect/with that accent.
When I try to speak with a UK English accent, I like to pick an actor I like and copy their way of speaking. It’s easier than just trying to “speak with an accent.”
That’s my grandparents (or, rather, was, my grandparents). My grandfather’s accent was worse, but he came over as an adult. My grandmother came over as a pre-teen, so her accent was slight, but noticeable if you paid attention.
It varies. There are certainly people that, with a fair bit of work, manage to shed their accents. I had a colleague who was German and claimed not to speak English well until he went to grad school in California. He married a girl from there and, if I hadn’t known better, would have assumed he was from California. Then they divorced and he married a German woman. By a year later, he had a noticeable German accent. I knew three sisters who immigrated to the US (from Latvia) at ages 10, 12, 14. The eldest, despite getting a PhD in English, always had a fairly thick accent. The middle one had a light accent and the youngest, as far as I could tell, had no accent at all.
I have a couple of cousins who came to the US from Hungary at about age five. When they came they spoke only Hungarian, zero English. Now, as adults, they speak perfect American English so that nobody would ever know they weren’t native speakers.
It might depend on more than just age when people immigrated. My aunt grew up in Iceland and came to the US when she was about 19 - she never really seemed to have an accent, certainly not a heavy one. But I suspect she spoke English before she ever came to the US - her younger brother who visited for the summer sure did.
I hope it’s James Mason.
Oh, man, would I look funny. Ha.
There’s a lot more to sounding like a native speaker than nailing the phonetics. Prosody is key to sounding like a native, and it’s rarely or never taught. A “thick” foreign accent that is difficult to understand is more to do with prosody than phonetics.
Dialect coaches talk about “oral posture” - a way of setting your jaw, tongue and lips that will produce the characteristic sounds of a dialect or language. You don’t start by learning to copy individual sounds, you start by adjusting your face, and the right sounds start to come out!
There is an excellent series of videos on YouTube by Dr Geoff Lindsay that is relevant to English learners wanting to sound like a native, and to anyone interested in linguistics.
Here’s voice coach Erik Singer talking about oral posture in the context of Claire Foy playing Queen Elizabeth. He describes oral posture as “the logic that holds the sounds together - the individual sounds arise out of that oral posture”.
An older college friend of mine was a Swedish immigrant to the U.S. as an adult through marriage. She still had a noticeably thick accent, despite speaking nearly flawless English. However she raised her two American-born daughters fairly intensely as bilingual from birth, only speaking Swedish when they were alone at home and visiting back home in Sweden regularly. Not only did they have perfect American English as one would expect, she claimed their Swedish accents were pretty perfect as well, to the point where other Swedes assumed they were native.
My parents are Polish. Same deal as yours in re: accents. They’ve been in the States for 50 years now, and both have very strong Polish accents when they speak, and their vocabulary is probably around 8th grade.
My grandfather was born in the US and moved back to Poland when he was 7. He came back when he was in his late 40s, and died in his late 90s. I have never even heard him speak a word of English, even though he presumably learnt it as a kid.
Meanwhile, when I lived in Hungary, I had a friend from the UK who moved to eastern Hungary for an English teaching job in his early 20s, where he was forced to pick up the language, as almost nobody spoke English in the area he was at (I think Hajdúnánás). Within a few years, he was speaking absolutely flawless Hungarian. He had been monolingual before. I’ve been at bars with him in Budapest where natives would come up to him and think he was pranking them when he told them he was English. I’ve seen it multiple times. They would remark about his Eastern Hungarian accent, though. He is, of course, now a translator and interpreter.