Brewer

Captain Brewer is a US National Guard in Call of Duty: Modern Warfare 3: Defiance.

Recapture
Brewer and his group were sent to Alaska to carry out wilderness survival training. However, Command contacts them and redirects them to recapture vital resource facilities under Russian Occupation.

Split personalities?
In the Mission "Overwatch", "Brewer" appears as a British SFSG troop. He shares this trait with Sgt. Vargas who has also been turned into a British SFSG.

It is most likely this "Brewer" and "Vargas" are totally different soldiers as: their accents have changed from an American to a British accent, they are outfitted differently ("Brewer's" goggles are red, not orange and "Vargas" now wears goggles) and as mentioned above, they are mentioned as "Brits" by Command, but are part of the US National Guard in the first two missions "In the Wild" and "Isolation". It is most likely they were meant to be different soldier's, but named the same by mistake.