watched the Eternals trailer last night and my wife says, "He's got an accent?" when Richard Madden started talking. They showed him again shooting the eyeball lazers and she's like "what the hell is this? when did Bucky get all this?" and I had to explain that it was not Sebastian Stan but someone else entirely.
side note: someone who's been around for thousands of years would lose their accent eventually. but since they appears to simulacrums anyway maybe that doesn't matter.