Fridge Brilliance: In the two films, the main antagonist happens to be someone whose 'nationality' is to the 'opposition' of America in the Revolutionary and Civil Wars. Ian is British and Mitch is from the American South.
Abigail's password is "Valley Forge", which, although somewhat easy to guess, fits with her being a historian and having an interest in George Washington (as witnessed by her collection of the buttons), but Valley Forge might also have special significance to her as a German-American because of its connection to Baron von Steuben.
At the end of the first film, it's revealed that Agent Sadusky is a Freemason, tasked with protecting the Templar Treasure. So when you see him him fidgeting with the spectacles, he's showing Ben how to use them.