I know the M26 served in the ETO for roughly 4 months until Germany surrendered in April. It served in very small numbers, and never took over for the M4A3s it was supposed to replace.
It later served in Korea, though it would take a while to bring them into the country in any meaningful number. Most of the fighting was done by M4A3E8 Sherman Easy-Eights, which were approximately equal to the North Korean T34/85. The development of the Pershing was used in the development of the Patton line of medium tanks.
Considering the Pershing saw only minimal service in World War II, and was not deployed significantly to Korea, was it in anyway influential to the conflicts it took part in?
Put bluntly, no.
With only a score of the things partaking in ww2 as a field trial, you can imagine how much influence they didn't have. The effect was probably more moral "Hey, we have something which can take on Panthers on equal terms, I heard they've started arriving, maybe we'll get ours soon." i'm actually at something of a loss to think of any engagement where the Pershings did better than a Sherrman would have. For example, of various famous engagements, the one known time a Pershing met a Tiger 1, the Tiger won with a lucky shot. The duel in Cologne saw the Pershing punch through the side of a Panther, something the 75mm and 76mm tanks could do, and at Remagen, they had to be left on the West Bank of the river as they were too heavy to cross the damaged bridge that the Shermans could.
A better argument can be made in Korea where they provided a pretty good punch against North Korean tanks. Not that the M4s were incapable against the T34s either, mind, so it's interesting to speculate on the relative advantages of the gun and armor vs mobility and reliability. Either way, once the North Koreans generally ran out of tanks, the argument for keeping the Pershings with their questionable reliability ran dry as well. That said, M26 was a very good stepping stone for the far more impressive M46, so it's effect was not insignificant there.