Complex sentence: During WWII, Spam was not only eaten but was also incorporated into many other aspects of the war (grease for guns, can for scrap metal, etc.); it was so prominent that Uncle Sam was nicknamed "Uncle Spam".
Split into simpler sentences: During WWII, Spam was not only eaten, but was also incorporated into many other aspects of the war front (grease for guns, can for scrap metal, etc.). In fact, it was so prominent that Uncle Sam was nicknamed "Uncle Spam".