Hi. I think the details of what the author said were not included in your post. I researched and found similar question but with the additional information. Here's my answer:
According to the author, the conditions in Europe during 800's was chaotic. The Frankish Empire was disintegrated to federation of feudal lords, Church did not have power, knights forcing the peasants to pay taxes. Muslims controlled Spain.
A. Asralobe i think im not 100% sure
It was a massive war thousands of people died and the U.S population drops massively so it hurt the U.S badly
