How come it can be in every state?
Not familiar with USA im from Sweden.
We only have one Gothenburg here for example.
Springfield, Mass in the U.S. was seen as an important place in government, and manufacturing during the 1700's - 1800's, so many places were named after it in honor. Also Springfield is a common surname in the States, so many of the smaller Springfield's are probably named after a famous Springfield that lived there at one point.
Springfield, Mass, itself, takes the name from an area in England, were the first settlers were from. That's common practice in the States too.