Well based on all the posts maybe I am simply wrong. Certainly it would appear that it is not true for cities in Scandinavian countries. So maybe it only seems to be true in English speaking countries.But I found 18 countries ending in s and other than three ending with suffixes "lands" all have a vowel preceding s.
SO I like you believe there "is a sensible answer."

However, it can't be important and I thank all of you for taking the time to answer.

FYI I got into this when I discovered that Solomons, Maryland was named after a man named Solomon and wondered where the "s" came from.