The U-2 is an aircraft. If you believe it would carry 1950s style sensors over Iraq, I have a bridge to sell you. I suspect that any attempt to shoot down a U-2 would be met by some resistance, to put it mildly.
They have tried several times. They can't do it or they would have.
When I was in the Army they would tell us when and on what track a U2 was passing overhead. We could hardly track them let alone try to shoot one down.
They fly in excess of 70,000 feet.
Russia tried for years before they shot one down.