Hello!

First of all, we do not allow questions that covers all of history, is of a speculative nature of a 'what if' nature.

But I will give you an easy answer to avoid leaving you empty handed.

First, I am curious if this hypothetical is believed agreed with by historians.

No. Dan Carlin is just an entertainer and is essentially speculating. Historians do not sit around and wonder if one army could defeat another army from the future. Speculation is absolutely forbidden and is not allowed in academia nor is it allowed on here.