I like it, a nice brainteaser, but there seem to be quite a few valid answers missing. Jamaica = 18, Myanmar = 14, Denmark = 14, Bahamas = 14, Bolivia = 12, Bahrain = 12.
There's no rule that words can only be 7 letters in Scrabble. You can only play 7 letters at a time, but you can use existing letters to make words of up to 15 letters (the size of the board).
I'll say that 9-15 letter words are almost never played in Scrabble (although possible). In professional Scrabble, 8-letter words are very common as a bingo using all 7 tiles and an existing letter on the board. I can see not wanting to add 9-15 letter countries, but I don't know why 8-letter countries are not included.
The full name is not "Czechia", but rather "Czech Republic", meaning that it doesn't count. Please fix this. You should also consider making a caveat about Myanmar, since it can also go by the name of Burma, which doesn't make the list.
Hungary - 14 also is one