Buy Barry Fell’s books, if you can find them.
I have America B.C. and read it some time ago. I also recommend it. I found it in the same very useful Used Book Store where I found Gordon's book. In fact they also had a hardcover edition of America B.C. (different reviews at 2nd link) on the shelf when I picked up the Gordon book.
I think it is interesting that so far I have seen virtually no overlap in the two books. This either due to my faulty memory, or that there really isn't very much overlap in the evidence that each presents for early contact between east and west.
ML/NJ