Good to see this this type of quiz again! What happenes to place like French Guiana and Puerto Rico, do they just "not exist" as far as this quiz is concerned?
If we include overseas territories and departments, then Netherlands at Bonaire (88 km / 54 miles), France at Martinique (420/261, closer than French Guiana), UK at Montserrat (638/397), and USA at US Virgin Islands (656/408, closer than Puerto Rico) all come onto the list.