Thumpalumpacus
Major
Have GHWB firmly and clearly tell Saddam not to invade Kuwait in 1991 and much of where we are now today (GW1, GW2, 9/11, WOT, Afghan/Iraq occupation, Arab Spring, Syrian collapse, refugee crisis, etc.) would be different.
I seriously doubt Hussein would have listened to such a warning. He was under pressure domestically from the still-huge expenses of the eight-year war with Iraq, and had already spent domestic political capital decrying the Kuwaiti possession of the oil-fields he eventually used as his casus belli. To back down at that point could and probably would have been seen as a sign of weakness, encouraging a coup or even assassination.
Now, it's true that had he not invaded, the picture in the Mid-East would most certainly look different. But I think he was decided upon his adventure well before the fateful conversation with April Glaspie.