You wrote, "Johnathan Cahn wrote a fictional novel based on his reassembly of history assuming certain passages of Scripture apply to America." The problem with that statement is that, in fact, you are assuming that he is reassembling history, assuming that certain passages of Scripture apply to America. If you took the time to read the book, you would discover that he merely points out many undeniable parallels between ancient Israel and modern-day America. I have read The Harbinger myself and found it very compelling, and although I have also read many critiques of the book - often written by those who have not read it - I have not read anything suggesting that Rabbi Cahn got his historical facts wrong.
You also wrote, "The Harbinger contains a lot of info involving what Cahn has read into Isa 9:10 and read into American history." Without having read the book yourself, you are not qualified to say that. I don't doubt your scholarship at all, but you are expressing an opinion on something without doing your research in this case.
Please read The Harbinger first, then come back and give us a point-by-point refutation of what he got wrong. That approach would be much more helpful.
Thank you,Lydia F