Rock N' Roll existed long before Kid Rock, and will carry on long after him. Of course, that's not to say he's irrelevant. He's got a style and approach that connects with a lot of people. However, I don't think his contribution is unique, and that many artists in Rock N' Roll play the same kind of music that he does. I think it's the other way around: Rock N' Roll changed Kid Rock, Kid Rock did not change Rock N' Roll.
There are many artists who have left their mark on Rock 'n' Roll. Kid Rock is arguably among them. Would the culture be changed if he had never picked up a guitar or a mic? Absolutely. Would that be better or worse? No one knows. Kid Rock may have inspired someone to be a little more like him, or a little less like him just enough to make that vital change that inspired greatness later. This is the butterfly effect. No one thing within a system can exist without impacting the system on some level. No matter how large or small that change may be, the change is irrevocable.
Kid Rock's first known commercial success occurred in 1998 with the album "Devil without a cause" which sold 13 millions copies. Rock 'n' roll originated and evolved in the United states in the 1940's and 1950's. So by the time Kid Rock began to perform Rock 'n' Roll was already an established music form for close to 50 years. So If Kid Rock had never begun performing the musical history of rock 'n' roll would not have been irrevocably different.
No, I do not believe that rock 'n' roll would be any different if Kid Rock had performed or not performed. I really do not think he made a real difference in this genre in reality. He is, however a very popular person in the media and the rock family, but he is just another rocker in a long list of rockers.
I do not believe the history of rock 'n' roll would be dramatically different had Kid Rock not become the performer he is today. While he has a large following, rock 'n' roll was already a formidable force long before he came along. If he weren't in the industry today it is possible that other artists would have merely filled the place he currently occupies.