How did the battle of Thermopylae affect smaller countries?

Answer 1

The Greek city-states which did not go over to the Persian side had tried to win a sea battle against the Persian fleet to remove the naval threat to their cities. Blocking the pass at Thermopylae was a ploy to force the sea battle at nearby Artemesium. The sea battle was lost so they had to try again at Salamis. Until this sea threat was removed, the city-states had to keep their main armies at home protecting their cities against amphibious attack. So Thermopylae failed in its purpose. Salamis succeeded, and the following year the cities sent out their armies to join up at Plataea where they defeated the Persian army and its Greek allies, and the invasion was over.