We’re Americans who moved to France 20 years ago. Our kids were 7 and 2 at the time and the 3rd was born here. The 2 younger ones (now 19 and 22) have literally a French persona and an American one. One can’t be bossy/whiny/mean IN ENGLISH- only in French. The language they speak (and to a lesser extent me and my husband) absolutely changes their personalities to be more culturally aligned with the language. I’ll say things to French people that I wouldn’t dare say to Americans (political debates are a great example), because I can and they can handle it. Generally, communication isn’t as sugar coated in France. This bothered my American family when we’d visit and I’d speak my mind about something. Learned that lesson pretty early on!