DOES TIME POSTING REALLY MATTER ?

I have 2 years experience in content creation tiktok , and an account with more than 300K followers .. but still can't fix that . i'm trying to reach a us audience but i get engegement from south africa and that is what hurts my RPM , so i think it's the time postng effect . I REALLY WOULD KNOW YOUR THOUGHTS , i'm talking to experts please .