The Star Spangled Man?

Stephanie Roberts wanted to serve her country. She wanted to be a soldier. Only problem was she was a 90 pound, asthmatic woman. The Woman's Land Army wouldn't even take her. After her fifth attempt to enlist she gets the chance of a life time. She agrees to Project Rebirth and becomes Captain America. And, yeah, the world thinks she's a man but at least she's where she wants to be.