Here is the short version to your questions.
1. It is like trading family stories. Knowing your heritage, your family's recipes and being able to move them from generation to generation is like a birthright. It is something tangible that your parents can leave as a legacy to generations beyond.
2. Communication has led to a diversifying of world food customs. Being able to understand how people eat in other areas of the world allows us to try and make their food and use their spices and cooking methods.
3. Fusion is the mixture of different kinds of cuisine. Fusion is generally a mixture of cuisines from different continental regions more than anything else. There are exceptions, but there are a lot of people that do asian fusion foods as they westernize and update traditional asian cuisine.
4. The US has always been considered a melting pot outside of the culinary world. People from all walks of life and from all over the world immigrated to the US for whatever reason (religious freedom, political freedom, etc), and this has consequently led to a huge diversity of American peoples. This effects us culinarily speaking because all these different cultures co-existing has led to a melting pot of foods, flavors and people.
5. Ethnic restaurants have gained popularity because there is so much more emphasis on global cuisine in today's world. People are always looking to find healthy, delicious alternatives to how they eat, and the standard "american" cooking has been globalized as donuts, hamburgers, and fast food. People all over the world eat healthy and have different delicious ways to prepare food, so people are looking to other ethnicities for culinary inspiration. The media markets it, and people want to try new things.
6. Food preparation has been more and more creative with the movement of technology. This could be anything from the ability to refrigerate and freeze foods, to also being able to have an in-home deep fryer, or whatever else is commercially available. Restaurants also find a need to stand out, so that they will attract customers, so business is also a huge motivator for food preparation to become more creative.
Hope that answers your questions.
