This may be macabre, but if I were the Royal Family, I would be extra careful with letting William and his children all travel together. (Before the *********, they all took a Flybe flight to Scotland!

)
I do think it's a legitimate issue that you have a prince who, at this point, seems to be developing stronger ties to the US than the UK. Archie qualifies for dual citizenship and is (debatably) a "natural born U.S. citizen"; their daughter will be indisputably a natural born US citizen. The children are presumably going to grow up as Americans and have American accents

, with stronger ties to the US than the UK. If, through some tragic disaster (plane crash, terrorism), they somehow become heirs to the British throne... it is an issue.
(Yes, I do know about George I from history -- and the bloody Life in the UK test

-- but times have changed.)