The flag you see at the end of the episode on the car is in fact the flag of Switzerland and not the flag of the Red Cross. The flag of the Red Cross is a red cross on a white Background. The flag of Switzerland is the opposite: a white cross on a red Background. They look almost the same because the founder of the Red Cross was Swiss and he took the flag of his home county for his organization, but in reverse colors.
Gibbs phone Slone at 07:30 on 22nd December, which would only be about 7 minutes after sunrise, while in Afghanistan it would be less than an hour from sunset. Both places look too bright for those times.
The senator says "there's a plane leaving in the morning...", yet they are still en route in the humvee after it's dawn in DC. That would make it late afternoon in Helmand, and the senator would have missed the flight.
McGee states the odds of rolling a 2 on a pair of dice is 36 to 1. Actually, even though the probability is 1 out of 36, the "odds" are 35 to 1. As an MIT grad, McGee should have known that.
Chet refers to hot air blowing in his face all day (in the Afghan desert, and his marriage) in his opening joke. All personnel are wearing light clothing. It's stated that it's 22nd December. Given that it's daylight in DC, it must be near sunset in Helmand. In December in Helmand, the average temperature is around 9 degC, and cooler towards night, so a bit cold for light clothing. Also, there would likely be snow on the ground in places.