Complex sentence: Wedding soup is a soup that is especially popular in parts of the Northeastern United States, as well as in Pittsburgh, Pennsylvania where it famously is a staple in most local restaurants and is even served in local McDonald's fast food restaurants.
Split into simpler sentences: Wedding soup is a soup that is especially popular in parts of the Northeastern United States. The Northeatern U.S. city that is most well known for it is Pittsburgh, Pennsylvania where it famously is a staple in most local restaurants and is even served in local McDonald's fast food restaurants.