As far as I could see from Google Maps,Dover (Delaware) doesn't have any 'White cliffs',and the 'White cliffs' in Dover(England), aren't 'home' to Bluebirds,so I wonder how the song 'came about'.
The composers must have made quite a lot of money out of the song,just Vera Lynns' version alone must have 'raked it in for them',and at 97years,she is in the UK Top 40 Pop Charts again,with another 'War-time' compilation!