Does America even have a national dish? I've never heard of a dish that I would say is specifically American. Claims are made for Apple Pie and the Hamburger / hot dog but I don't know that either can really be claimed beyond the application of a bun.
In South Africa the main celebration is having a BBQ which is called a BRAAI in the Afrikaans or Dutch language, with mayonnaise in a potato salad, in Croatia it is smoked meat with green cabbage and potato boiled and eaten, tastes great with the slightly salty smoked meat and with the combination of the cabbage and potato
Here in the UK it was traditional to have roast beef with two veg, so much so the French called us the roast beef's (in French of course). With the onset of engineered multiculturalism its more likely that we have chicken curry or a stir fry. Many young see McDonalds as a staple diet and the problems with obesity and malnutrition can be attributed to the lack of good old home cooking.
Well we have a lot of dishes that are made here and which are good. If I have to pick one I think that would be Sarma (Cabbage with meat). It is made by rolling the cabbage leaves around the meat and than you cook it