I would question whether some of the territories listed above are countries in their own right. For instance Saint Helena, Saint Pierre and Miquelon, Scandinavia (certainly not a country, a part of Europe consisting of several countries.), Svalbard; some of the others look dubious also.
Spain, sweeden, syria, Saudi Arabia, Samoa, Somalia, siberia?
There are only 26 countries starting with letter S (please excuse any incorrect spelling):
1. Serbia
2. Slovenia
3. Slovakia
4. Spain
5. San Marino
6. Sweden
7. Switzerland
8. Senegal
9. Suriname
10.Swaziland
11. South Africa
12. Seychelles
13. Sao Tome and Principe
14. St Lucia
15. St Kitts and Nevis
16. St Vincent and the Grenadines
17. Singapore
18. Syria
19. Sri Lanka
20. Solomon Islands
21. Samoa
22. Somalia
23. Sudan
24. South Korea
25. Saudi Arabia
26. Sierra Leone
Switzerland, Spain, and Sweden
There are no countries (in English) with names five letters long with "s" as the second letter.
segoe script
Sage.
Sequoia
Silencers
King Solomon
Shelby Helmuth
slayer
Some Spanish names starting with T from the 1500's could include: Teresa TomΓ‘s Trinidad Teodoro
J.D. Salinger is one.
Serbia, Sweden, Switzerland, Slovakia, Slovenia and Spain are countries in Europe that begin with the letter S.