They won't be playing the anthems. How anyone can say that a couple of thousand Calzaghe fans will affect his performance and guarantee that he'll "lose his cool" when he's fought in front of MUCH bigger audiences before, is beyond me.
His other opponents did not put him in a position where he had to make the fight a good fight. I don't think its the pressure of big crowds, I think its the pressure of looking good for your first fight on US soil, in Las Vegas no less.
Most fighters testify that when the fight actually starts the crowd and venue become an irrelevance. Besides the crowds in Vegas are usually quite subdued, I can never really tell who the crowd favourite is when watching US fights. The Hatton crowd are a bit of an anolomy. Calzaghe will take support no doubt but not the flag waving national anthem booing football style crowd that followed Ricky. It wasn't any crowd participation that overwhelmed Hatton either it was the right hands that kept snapping his head back that got him flustered.