Basically the two campaigns each show what would have happened if its respective faction would win the war  As such theyre two separate stories  As for which campaign ending is canonical the sources we have available say that both Tiberian Dawn and Red Alert  follow on the events of this games Allied campaign  However RA and by proxy RA dont take place in between RA and TD according to former CC designer Adam Isgreen but exist in a separate universe altogether rendering them spinoff games by definition  Hope that cleared things up