Complex sentence: Although he does not provide the voice, Arnold Schwarzenegger is President of the United States rather than then-President George W. Bush because "in two years... the film (would be) out of date".
Split into simpler sentences: Although he does not provide the voice, Arnold Schwarzenegger is President of the United States in the film. He was chosen instead of the then President George W. Bush because then, "in two years (...) the film (would be) out of date".