Strictly speaking both congregational and presbyterian are labels for theories of church government. In practicality, in the US, they are labels for more. Partly this is the history of New England Christianity and how it spread throughout the rest of the nation, partly the internal logic of theological systems and how they grow and evolve.
the New England Puritans were congregationalist in church government, partly due to theory, but mostly due to the conditions in England where Presbyterianism was tied strongly to one side of the English Civil War. Dissenters in several flavors were dissenters from the Church of England, some dissented for theological reasons, some for institutional reasons, the CofE is hierarchical, it's opposite in most people's minds is congregationalism, with presbyterianism a half way compromise between the two.
Because of the related ethnic waves of immigration into the US, Presbyterianism had strong ties to Scotland and to the Scotch-Irish. There is a Welsh and English Presbyterianism, and a Continental (mostly Dutch) one as well.
So historical we have competing waves, ethnically based in part, arriving at different times, at different places on the coastline. The first big problem occurs with the westward movement, both NE congregationists and Presbyterians lost out big time to the Methodists and others who followed the settlers. This resulted in several reunions and campaigns to 'win the West'. As a result much of the mid West was congregational with reformed roots-the precursor of the bible church type of congregation.
the big problem with wide view analysis like this is that congregationalism depends very heavily on who was the pastor in the past, and who he is now. The congregations reflect people's personalities more than presbyterian or hierarchical structured churches which tend to be more doctrine orientated than personality.
so as a rule of thumb, a presbyterian church ought to be in alignment with it's denominational standards, and a congregational church is a mixed bag until you get to know the leading members and their theology.
