It's a very long sentence with a lot of information, but it is still only a simple sentence (option b): it has only one verb (taught). In order to qualify as a complex or compound-complex sentence, it would have to have at least 2 phrases, each with a different verb.
It shows that the war resulted in a new illusion of omnipotence."In April 1917 the illusion of isolation was destroyed, America came to the end of innocence, and of the exuberant freedom of bachelor independence. That the responsibilities of world power have not made us happier is no surprise. To help ourselves manage them, we have replaced the illusion of isolation with a new illusion of omnipotence" Barbara Tuchman
