After many searches on google about the french voice of Captain America in Ultimate Avengers and Ultimate Avengers 2: Rise of the Panther, I found that Jean-Pierre Michael doing the french voice.
Why I was searching the french voice? Because all the french voices of the animated movie Ultimate Avengers were the voices of the actors: Bruce Banner had the french Edward Norton's voice, Iron Man had the french Robert Downey Jr.'s voice, Nick Fury had the french Samuel L. Jackson's voice, etc..
Then I've started to search, on the official website of Jean-Pierre Michael, an actor name of someone who could fit the Captain America's cast, knowing they search an actor between 23 to 32.
I found only one actor: Brendan Hines. He is 32, american and with some training and blond hair, he could be a nice Steve Rogers.
He played Andy Goode in Terminator: The Sarah Connor Chronicles.
He currently appears in the serie Lie To Me, with Tim Roth (Emile Blonsky/Abomination in The Incredible Hulk!).
Here's his picture:
What do you think?