This a valid question indeed!
In a very convoluted way one could come up with that statement but you have start by ignoring everywhere but the USA. Were all oil and gas production to stop in the US, millions of vehicles would be taken off the road, thousands of portable electric generators that supply power to drilling equipment needed to drill the oil. All of the equipment used for exploration would be parked a long with all the equipment need to service wells. Basically it’s say get rid of all the energy consuming, emission producing vehicles and equipment need to produce energy and you reduce emissions.
Now does that actually change anything on a world wide basis, absolutely not, but it would reduce US emissions. I might also add that it would leave the United States of America at it’s weakest point in history, 29 oil producing states struggling for revenue and millions of Americans unemployed. Which in my opinion would be the only reason one would pursue such a thing.