In this link, Past Unreal Conditional, user l'électeur has given an answer pointing to the tense issues in the original sentence given in the question, stating that ていた needs to be used instead of た:
If I had turned right back then, I wonder what would have happened.
l'électeur has given the following corrected sentences:
「あのとき右に曲がっていれば(or いたら)、どうなっていた（の）だろう(or のであろう)。」
However, I would like to know why exactly ていた and not just た must be used for both 曲がる and なる. I am aware that ていた expresses a state while た focuses on the action, but I simply cannot comprehend why one would choose to focus on "the state of turning right" rather than regretting his decision of not "taking the action of turning right".
I have done some research on these tenses myself, and one source I have found is the following question, which I have derived the "state" vs "action" idea from: