(Disclaimer: I do not claim to own Hetalia, or its characters.)
Prussia was the first to go. It was weird to say the least, a country dying. None of them had thought it quite possible. It wasn't until Greece fell ill and later died that it actually hit home. (Turned out another had died before that though. Someone no one could ever quite remember...)
Alfred looked back on how naive they'd all been in the early days of their downfall. They were thought to be invincible, immortal, sure, but it was stupid to think that. Him, being the hero after all, should have known it best of all.
Over the course of the next year all the nations were halved. Countries were dying on a regular basis, for no reason in particular. Some grew ill, others suffered fatal accidents, ones they should have easily been able to survive.
However, America had troubles of his own. Not only was he growing weaker but his children were falling ill as well. His little Cali was doing the worst. Alaska and Alabama weren't doing much better.
Soon there were very few of them left. Himself, England, and Germany. Spain and France had died last year, having been five years since Prussia's death. They all knew it was only a matter of time.
America thought back upon the many centuries of his life. They'd all been foolish thinking they would survive. Now he wished he'd been one of the first to die. It would have been better than watching all his friends die, his children slowly doing the same. For once the hero had been defenseless and he'd let everyone die.
So as America laid down to die he thought about all the accomplishments through his life and really, it added up to very little.