France is widely considered the best. I choose American because it encompasses so much great and varied food.
I like weird and seafood, preferably together- Thai, Sri Lanka, NW Indian, Vietnamese and western Mexican.
I can't speak for every country but I went to a restaurant in Spain that was in an old castle on top of a mountain. I had a steak from a cow that was raised free roaming on the mountain. No hormones or preservatives. It was the best meal I've ever eaten in my life and I'm not even a big fan of steak. Over there they tend to eat local food from the region, ie if they live near the sea they eat local fresh seafood, if they live in the country they eat from local farms etc. The food is so fresh and good. I think a lot of Europe is like that.
I have been to over 50 countries in my life and my ranking is this: 1. USA: For the reasons people have already posted, we have the best variety, but also because we do steaks better than anyone, anywhere. 2. Italy: The best of one style of cooking, hands down. The way they eat is also so awesome, course after course, all amazing. 3. Turkey: Meddateranian cooking, Lots of grilled chicken, fresh salads, olive oil, amazing flavors. Baklava is so damn good too. Lots of other great food, but this would be my top 3.