Some landlocked nations would be virtually unaffected but the sea level itself, though. There's also countries that have most of their main cities in the interior (Russia being one).
Also remember that a "main" or "important" city before the crisis is a mere refugee source after a worldwide crisis.
Before a crisis, the capital of the worldwide financial system and a major world trade port is kinda important. After a crisis ends both the financial system and world trade, its little more than a source of refugees.
If you want to wargame it out, look at the effects on agriculture. The US would be pretty much unaffected, sure we'd lose Florida and N.O. but we'll still have wheat and corn in the midwest, uninterrupted. Rice cultivation and historical hydraulic empires like egypt might have a little more trouble. Of course it depends how slowly it happens. The total solar energy striking the poles, even if it magically 100% perfectly went into ice melting, would take a heck of a long time. Its not going to be like tossing an ice cube into a campfire, no 65 meter tidal wave of water would result.
The capital effects would be interesting. So... your nuclear plant is 40M ASL today, and after the melt it'll be 25M below sea level. Well, at least it'll have plenty of cooling in an accident.
Some cities are important in every category though, just by virtue of concentrating a lot of the population. For instance the US would be pretty much in complete disarray for decades if the coastal cities of California and the East Coast were just wiped. They concentrate a lot of the power in every single respect, and also the brains.
Well, people from the affected countries will be forced to migrate away from sea, so I don't think the landlocked (or large) countries would be safe - on the contrary, they'll be facing a massive invasion of desperate people. This might turn into a "nuke'em all or get conquered" scenario.
This simply wouldn't happen. These countries would have to deal with such an internal collapse they wouldn't have much of an organised military left. Also, there would be widespread division - the powerful wealthy individuals would be welcome to other nations and the ones left would have no means to invade fuck all.
