There were no bridges. Lee fought with his back to the river. Packhorse/Boteler’s Ford was the only way out. McClellan was clearly paralyzed by the weight of decision. He might have made an admirable chief of staff but was temperamentally unsuited to command. His chronic tendency to credit Lee with vastly exaggerated numbers is the iconic symptom. At Antietam, he was also hyper-sensitive to a theoretical threat to his open left flank. After the Seven Days and Second Manassas campaigns, one can understand the sensitivity; leave a flank open and Lee would find it with half his army. But McClellan lost all perspective.
My mistake. I hadn’t thought about this particular battle since I wrote a paper on it back in 1993. But I have always been totally fascinated in the possible change in US history if McClellan had been more bold.