How does Willy's desperate quest for the American Dream in "Death of a Salesman" resemble a religious crusade?
Although I can see how you might read Willie's behavior as a religious crusade, I suspect that his behavior much more closely resembles delusional obsessive behavior, and I would hesitate to associate that with a religious crusade. Willie has "bought into" the most shallow form of the American Dream, the economic level; he defines success in terms of business success and outward appearance (the Adonis thing) rather than a personal integration. He has his own "crusade" when he attempts to spread this dream to his sons, but his will not offer redemption, just the perpetuation of his delusion.
And please do not read this as judgmental of Willie. I believe he stands for that portion of the American Dream that many of us have fallen into, the part that is opposed to Thoreau's "Simplify, simplify, simplify."
For one to engage in a religious crusade, he must have belief and faith. Willy believes that the American Dream can provide him with happiness. He also continues his faith in the Dream throughout the years when it is obvious the Dream has failed him. It is his religious fervor in following the wrong dream that destroys him. He also tries to convert his sons, especially Biff, into buying into the Dream. And so you have a close metaphor of a religious crusade to Willy and the American Dream!
I have to agree with #3 on this one. Whilst there definitely are some similarities, above all I would say that Willy is more delusional in his unswerving devotion and faithfulness to the American Dream - even to the point of his death. However, there is truth in what you say, as Willy kills himself to preserve the delusion he has fallen into - it was easier to do this than to face reality.