Can't find an exact match, best guess is a field-modified Half-Track Car M2A1 , or "artistic license" to have the combination of features shown. Any U.S. Army half track specialists care to chime in?
ezekill said: I remember a variant of this carrying quad-50's or was it Bofors cannons.
That was the M3 (or to be specific to that patform, the M16 MGMC). This doesn't look quite like that vehicle either...though it is closer. It's that weird cupola on top that has me baffled...it looks like how the Germans mounted the machine guns on the tops of their tank turrets.
EDIT: Looking closer at that Wikipedia link, the second picture is a version that has an armored cupola. So perhaps it is an M3A1 with the proportions a bit messed up.