The term "asymmetrical warfare" has a specific meaning in military circles--it specifically refers to guerilla and insurgency tactics (or countermeasures to such tactics). By analogy, I'm interpreting "symmetrical war" to refer to a lack of such tactics.

The First Gulf War was fought as a tank, air, and infantry warfare model, much akin to World War II-style tactics. And actually, the numbers were a lot closer than you might expect; the Gulf Coalition was made up of ~1 million men (the majority of them US), with Iraq having about ~600-700k defenders arrayed against them. Actually, it was remarked at the time that it seemed a risky strategy, since conventional military theory generally has you wanting about a 2-3× manpower advantage to be able to overcome a defending force.

The Iraqis were arguably not particularly inferior in terms of technology--they were a petrostate after all, and able to buy the fancy modern weapons on offer from both sides of the Cold War ideological divide. However, their organizational capabilities were decidedly inferior. It's not entirely clear to me why their anti-air capabilities were completely ineffective, but the US was able to achieve total air superiority and it used this decisive advantage to completely eviscerate Iraqi command-and-control. In the actual field, the losses that the Iraqis sustained quickly turned to utter routs.