Obviously, the main difference is that Jewish food doesn't use pork or shellfish products, or mix milk and meat. Other than that, a lot of Ashkenazic Jewish food does indeed reflect the country it originated in, but it's gotten all mixed up here. For example, pastrami was originally strictly Romanian, but today it's just called "Jewish food." Also, there are or were subtle differences between the food of the various countries even when it's the same food. For example, Polish gefilte fish is sweet, Russian is spicy and peppery. Some things seem to be Jewish only--for example, the bagels, cream cheese and lox sandwich, which may have originated in the United States.