Indeed, both Willy Loman and Blanche du Bois are tragic figures who suffer from the "terror and fear" of self-delusion in their struggles against society which "degrades them." So, perhaps rather than focusing on the American Dream as a theme--which certainly exists for Willy--there may be more commonality with the characters in the theme of Individual vs. Self:

• Both characters deceive themselves about their appearances.

By placing shades over the lights and only dating Mitch in the evening, Blanche creates the illusion of youthfulness in her appearance; further, she dresses as though she were yet the Southern belle and she is flirtatious and proud of her girlish figure:

You know I haven’t put on one ounce in ten years, Stella? I weigh what I weighed the summer you left Belle Reve. The summer Dad died and you left us… (Act 1)

Similarly, Willy believes that he can be more successful if he regains his youthful look:

I gotta overcome it....I’m not dressing to advantage, maybe. (Act 1)

• Both believe that they can attain happiness outside themselves.

Willy Loman and Blanche DuBois seek false and shallow promises of happiness; Willy perceives material wealth as the keystone to success and contentment, while Blanche seeks attention and romance as a delight and marriage as security.

"Always dependent upon the kindness of strangers," Blanche delights in attention and romantic flirtation as a diversion from reality as well as a bolster for her diminishing self-esteem and as escape.

In Act 2, for instance, Stella instructs her husband Stanley to compliment Blanche,

And admire her dress and tell her she’s looking wonderful. That’s important with Blanche. Her little weakness!

Further, Blanche hopes to attract Mitch enough to get him to propose and, thus, bring her some contentment and financial security since Belle Reve has been sold to pay debts.

In Death of a Salesman, Willy feels that happiness is attained through personal success and material wealth, 

....I realized that selling was the greatest career a man could want. ’Cause what could be more satisfying than to be able to go... into twenty or thirty different cities, and pick up a phone, and be remembered and loved and helped by so many different people? (Act 2)

Like Blanche, he looks elsewhere for contentment. In Act I, for instance, Happy tells Biff, who complains that Willy mocks him, "He just wants you to make good, that's all." Even his act of suicide is intended to give his son's some financial security and himself some respect. He imagines a conversation with his brother about his funeral,

All the old timers with the strange license-that boy will be thunderstruck, Ben, because he never realized—I am known!—I am known...and he’ll see it with his eyes once and for all. He’ll see what I am, Ben!(Act 2)  

• Present and Past blur for both

Blanche and Willy retreat to memories and illusions of success.