Yeah, I have to say that the fall out is probably the reason that the president survived the episode.

It's one thing to cover up an attempted assassination of the president, but if the Winchesters were even just accused of the actual assassination of the president, there's no way they'd ever be able to show their faces in public again.
That was hard enough to believe after 'Slash Fiction', but once they'd be known as the murderers of the president.... the entire country would recognize their faces.