What's new in A Game of Thrones 2nd Edition?
Well, according to this post at BGG, the rules changes are


Unit counts - each house has 5 knights and 2 siege engines, instead
of 4 knights and 3 siege engines.
Setup changed to include various neutral forces tokens.
Wildling Attack cards added.
Garrison token of 2 for each house's starting position.
Play to 7 castles regardless of player count.
Wildling threat of 12 triggers an attack.
Messenger raven allows you to look at the top card in the Wildling Attack deck (OR replace an order).
Raiding a Consolidate Power order makes the target lose a power token (in addition to the raiding house gaining a token).
When playing your 7th house card, you get the other 6 cards back, but not that last one played.
Special raid order can remove a defense order, but NOT 2 orders.
Special consolidate power order can muster units OR gain power tokens as usual.
4 player game is played without Tyrell (instead of without Greyjoy).
Tides of battle cards.