US Army soldier: Wait! You know what you're doing?
Steve Rogers: Yeah, I've knocked out Adolf Hitler over 200 times.
When the action moves to England after the failed award ceremony, the British Union Flag hanging from the wall is upside down. The broad white band should be at the top left (nearest the top of the flag pole).
Before Steve Rogers exits the chamber that changes him into Captain America, the sound effect used for the machine winding down is the same as the sound effect used for the rocket pack shutting down in The Rocketeer, another of Joe Johnstons movies.