Sounds like a fun time!
Keeping in mind of course that what you propose means that you will have a sampling from the counter service or other walk up kiosks at a given country, yes?
So, Mexico: No real favorite of ours here, but many folks like the frozen margaritas and selections from the cantina.
Norway: Choose something yummy from the pastry shop.
China: There is a little walk up kiosk with a limited selection of items (tea based, mostly). If you've not tried bubble q tea, this might be a good opportunity.
Germany: Well, you can choose beer

or wine from the shop. There are many candy/sweet selections in the shop. A pretzel seems to be the favorite purchase for us here, but only if they are hot/warm. They've changed the choices at Sommerfest so much that we don't really care for the selection any longer.
Italy: There is the little kiosk of desserts and other sweet things. Chocolate covered strawberries are sometimes there. Give the gelato a miss though (at the "donkey cart"). It's not very nice.
US: We don't much like anything here

but there is the ever popular funnel cake!
Japan: Loads to choose from in the shop.

Be adventurous, try something like dried crab!

You can order a sake at the very back of the last area of the huge shop too.
Morocco: There are nice frozen drinks at the outdoor kiosk (with or without alcohol). I particularly like the tangerine one.

There are LOVELY "pastries" (little cakes and the like) there but a better selection inside the Cafe (toward the back). Try the little cake with almonds and tangerines on top.
France: A good chance to have a cheese plate from the bakery? There is still a nice selection of items to choose from here (although through the years the more interesting stuff has been taken from the menu). Wine is available. Or perhaps you'd like a drink from one of the outside kiosks.
UK: Well, they pull a pretty decent Guinness here!

Be sure you get it from the indoor Rose and Crown bar. There is a nice selection of pub food that you can choose from. We love cheese and there is the opportunity for another cheese plate here too.
Canada: Will be the challenge. They don't have much other than beer or popcorn at their walk up. There are some selections of treats in the shop though, so have a look there.
Hope that helps a bit. It's surely not extensive, but do enjoy your birthday at the WS!! It's a great place to celebrate!
