Ben Zimmer pulled up the 1966 citation that identifies Jim Murray as coining the phrase in Life magazine in 1950.
23 February 1966, Los Angeles Times, "The Old Breed" by Jim Murray, p. B1
I guess I'm getting sensitive in my old age. Getting the feeling people don't appreciate me.
It all began when I heard the guy on television say, "Well, it was Bennett Cerf who once said, 'Rooting for the Yankees is like rooting for U.S. Steel.'"
Then, Bill Veeck, in his latest book, "The Hustler's Handbook," notes "The Yankees should sue the guy who first said that 'Rooting for the Yankees is like rooting for U.S. Steel' because he articulated for so many people what they had already come to feel."
Ok, now, you want to know who said it first? You're looking at him. Old numero uno. James Patrick Murray.
You don't believe it? All right. Do you happen to have a copy of Life for April 17, 1950 around the house? Gen. Eisenhower is on the cover. He always was in those days. Open to Page 25 and you'll find a story titled, "I Hate The Yankees" by a guy identified as "James Murray, Time-Life correspondent in Los Angeles."
On Page 28, you will find the tell-tale phrase: "For my money the Yankees were and are super-champions for the same reasons General Motors or U.S. Steel or Standard Oil are super businesses. They have more fans paying more money than any other club in the history of the game."
On Page 32, you will find the sentence: "Anyone who wouldn't root for them (The Yankees) must have interred sentiment. Sentiment indeed. I would as soon feel sorry for Standard Oil because it was getting slightly the worst of it in a marketing fight with an independent gas station in East Podunk."
21 October 1953, Sporting News, pg. 1, col. 5:
Give or take a syllable or two, the most significant quip to come out of the World Series press box during the late departed classic was: "Rooting against the Yankees is like rooting against U.S. Steel." The author could scarcely have called upon a more powerful simile.
It ranks up there with the one coined after someone had dusted off Phil Rizzuto and in the next inning three rival batters had to sit down in a hurry to keep from being brained. The crack then was: "Throwing at Phil is like hitting a cop."
The last crack may expire eventually from disuse because there is only one Phil Rizzuto and he isn't getting any younger, but they're likely to be talking about, and linking, the Yankees and the nation's No. 1 steel corporation for some time to come.
6 January 1954, Sporting News, pg. 36, col. 1:
Best gag line in the stands came from Jim Little, the TV actor, who said, "Rooting against the Yankees is like rooting against United States Steel."