The footballer, who moved to the US to play for LA Galaxy, made the comment during an appearance on The Ellen DeGeneres Show yesterday.
"They actually really do [have American accents]," he explained.
"Every time we go back to London, which is not that often, my parents and Victoria's parents will say, 'Wow, their accents are really American now'.
"They're really into it. We live here now, it's an amazing thing for them. They are happy in their school and their lives."
He added that Brooklyn, 10, Romeo, 6, and 4-year-old Cruz were still getting used to the attention that he receives in public, saying: "It's still surprising because obviously to them I'm just Daddy."
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