Character mistake: In the Iraqi Desert, when the British soldiers speak of the casualties and losses, one of the British soldiers mentions the loss of the Belgian contingent and possible reinforcements, then makes a reference to the "Golan Straits"; there is no such place.
Factual error: Aliens are using TV satellites for their secret attack signal, making the TV picture quality poor. David shows the president how they do it by bypassing the curvature of the earth. However TV satellites don't work that way. They are "hanging" pretty much above their broadcasting area totally reflecting and spreading the signal back straight downward to earth. Turning the parabolic mirrors of the satellites to a different elevation would result in no TV signal on earth, not just a degraded one.
Continuity mistake: The alien saucer that arrives over Los Angeles is said to be approaching off the California coastline, yet it is specifically shown approaching from Imperial Valley, which is to the east/southeast of Los Angeles.