The President is told that the Haitian army has "two Bradleys with 120 millimeter cannons". The Bradley infantry fighting vehicle is equipped with a 25mm auto-cannon; the 120mm gun is on the much larger Abrams main battle tank.
It is possible, though unlikely, she is referring to the variant of the Bradley equipped with the 120mm mortar.
Sam's full name is Samuel Norman Seaborn. The large letter of the monogram on his shirt shows a large N in the middle, with two small S letters on the side. The large letter is traditionally the last name, and should be an S.
"Carrefour" is not French for "square" as a public meeting place. The correct translation of "Liberty Square" would be "Place de la Liberté", neither of which exist in Port-au-Prince.
The President asks if anyone knows Kenny's last name, and nobody seems to. However, both he and Josh learned it when they first met in the episode "Take this Sabbath Day" from season 1.