Tushonka is stewed meat that is stored canned, popular among Slavic people. It is commonly used in recipes with buckwheat, pasta, or eaten with bread. During the World War II this was one of the main dished used by the Soviet military. This method of storing meat, was adapted by Slavic culture and is still common in many countries of the Soviet Union. I think the closest thing that could represent Tushonka in USA, is Spam.
I often purchase the Army Brand Tushonka at a local Russian store. Army Brand Tushonka is delicious, but very fatty. Making homemade is an easy process, less costly and you control the ingredients.