You are confusing the PCA with the OPC.
The PCA left the newly formed PC(USA) in the 1972/1973 time frame.
You are confusing the PCA with the OPC.
Yep, it's confusing. The OPC first called itself something close to PCA (Presbyterian Church in or of America, I forget which), for a little while. The mainline denomination they split from sued over the name.
http://www.history.pcusa.org/sites/default/files/connection_900.jpg
The theology of RCA is (or was?) Calvinist, very close to the Presbyterian heritage, though they have their own terminologies ("Classis" Synod" "Consistory", etc.) Interesting footnote: The archival of Hope College is Calvin College of the CRC (Christian Reformed Church, more conservative), Their annual basketball clashes hold the national record for highest attendance at Division III basketball, something north of 14,000 fevered fans in attendance.
Ish - yes. I’ve been a member of the PCA for 25 years, and we claim Machen as our ancestor. We share the same seminary with the OPC.