Don't make me sing O Canada in response, eh?
But my responses (besides the obvious MURRICA) would be:
1: Spain. There's a lot of history in the components of this one, including the historical flag of the 5 ancient kingdoms that made up Spain: Navarra, Castille, Aragon, Leon, and Granada. (OK, let's just forget for a moment that Granada, which is represented as the bottom white portion with the flower, was actually an Arabic emirate for a while after the Reconquista... and Galicia, which is northwestern Spain north of Portugal, isn't represented)
[img=http://0.tqn.com/d/gospain/1/S/r/H/-/-/Spain_flag.gif][/img]
2: That would require me to be a little more cultured than I am. Cause pretty much the only ones I know are the US and Canada.
3: Would have to go with Spain again, for its varied and interesting culture and history. That peninsula has been influenced by pretty much every ancient culture group in Europe at one point or another, as well as numerous North African and Arabic ones. There's also so much wonderful architecture there.
4: Deviating from Spain for a bit... Canada! Hockey, eh?
5: OK, this one I will answer with Washington, DC. If you ignore the politicians, lobbyists, and lawyers... There's a lot of history and monuments to explore. The Smithsonian was one of my favorite stops there my last time around. And assuming it's not 80 degrees out with six billion percent relative humidity, the outdoor monuments are great too.