Top (M48 Patton):
The Tank at the top of the map is the one I personally think should be the main focus. Not only is it the stereotypical tank, it also stands as a symbol of the Americans at this time. A weapon of there own to crush any invading forces. Looking back at any B-movies, you can see that the variety of tanks is limited if not any variation (due to budget?). It was modified and carried over from the World Wars. When you look at the tank, you KNOW its an American weapon used for attack and defense.
Bottom Left (M46 Patton):
The Tank on the bottom left was used in World War 2 but wasn't discontinued till the 60s or 70s. Despite this, they were barely used and hardly ever scene. They were used more as a recon vehicle, so would they show up in our besieged city?
Bottom Right (M26 Pershing):
The Tank in the bottom right is a light tank used by the US army as quick response. Small and lightweight, they didn't pack the biggest punch but it was there image that was important.
'No fear!! The Americans are here to save you ALL!!'
It was all about image to put the public at peace. In regards to our movie/trailer, these would be the first line of defence, followed by the main force of the Heavy Tanks (top pic)