Burroughs Algol was based on Algol 60, Pascal was derived from Algol W which forked off from Algol 60 well before Algol 68, PL/I also predates Algol 68.
"History would have been much different if Algol 68 hadn't existed in first place."
Without the way Algol 68 went down, Algol W and the related events that gave birth to Pascal linage would never happened.
Likewise, PL/I adoption linage would most likely taken a different evolution.