Good quiz, but I had absolutely no idea about the sizes. Without knowing the size of at least one country it's pure pot luck, beyond the assumption the first is 'pretty small' and the second is 'slightly small'.
Maybe it's because I haven't had my coffee yet, but what is the difference between a country "entirely on islands" and a country "without land borders"?
That threw me too and I missed Japan because of it but Indonesia borders Papua New Guinea, Malaysia, Brunei, and Timor Leste but is entirely on islands while Japan doesn’t have any land borders.
Read the clue "whose name starts with H" and then for some reason I read the next clue as connected to that one and couldn't figure out why Honduras wasn't working. Wasted a lot of time trying different spellings thinking someone had made an error. Silly brain.