We have lived overseas for all of our DD1 and DD2 lives.
I have west London accent, not as pronounced as it used to be, but it is still there. DP has a more neutral accent (to my ear).
DD2 speaks like us, but DD1 (15) has a distinctly American sounding accent, maybe people would describe it as 'mid-Atlantic'
She's had it for years, but has not had a N. American teacher for ages.
I confess I do occasionally tease her about it, but it is of no serious concern of mine.
I just wondered if any other children also have picked up accents