As killers become more sophistocated, so do the defenders.
On the jeep page you linked to, do a find on "antidecapitation device". These were necessary because retreating Germans had a funny practical joke to play on GIs: they strung wire across roads right at neck level for Jeep riders.
Since the Germans did not bury anti-tank munitions in the roads set up to use as anti-jeep mines (which would have been incredible over-kill for those jeeps), there was no need to pack on a bunch of armor. Now there is.
I guess your larger meaning is that it is very unsafe for Americans to ride around in Iraq. Of course this is true.