Up to the last 10 minutes of extra time it was a one sided match, Belgium was vastly better and if it wasn't for brilliant Tim Howard it would have ended much, much worse for USA. That being said hats off to USA, hardly anyone gave them a chance next to Germany and Portugal, and they managed to keep off Belgium till the very end.
As for Argentina, I swear if it wasn't for Messi and perhaps Di Maria I highly doubt they would even reach this stage. They'll have to do noticeably better against Belgium, otherwise we might see a replay of quarter finals four years ago in South Africa.