In light of the Presbyterian Church U.S.A. (PCUSA)'s news-noted change in policy, Joe Carter wisely illustrated some key differences in theology and practice between the PCUSA and the Presbyterian Church in America (PCA). These are the two largest Presbyterian denominations in the States (and there are more . . .) and they have significant differences. Suffice to say, it's advisable not to make sweeping generalizations about Presbyterians.
I don't serve in a Presbyterian church myself, but I come from a line of family serving in the PCA, Evangelical Presbyterian Church (EPC) and a few other non-PCUSA Presbyterian churches.