Tough one. I think it would be difficult to point to any big national impact because of our geographic concentration. Lee Freeman might correct me but I think one of A Campbell's most concrete legacies was advances in education for women.
I don't know where you're from. I grew up on the staked plains in west Texas, almost to New Mexico. In those parts, I think there's been a big impact on education, at least in western Texas, eastern New Mexico, parts of Oklahoma. I'm not an ACU fan, but when it was started, I believe it was the first college that far west. Over the years, they turned out lots of school teachers who went to teach in lots of places other people wouldn't have been too eager to go to. I couldn't begin to list how many of my school teachers were ACU grads, but many were. I won't say that there wouldn't have been schools on the plains without the Restoration movement, but they wouldn't have been as good. That's really odd because nowadays, we have a fellowship where true learning is held in very low esteem by nearly everyone.
If you read through a cook book, there are lots of recipes that call for a little salt. When you eat the food, you don't notice the salt is there; but you'd notice if it were missing.
I'd say that where I grew up, the Church of Christ had that kind of influence.
And we can look outside the U.S. I could show you places in Mexico where life is radically different than it would otherwise be because of the Restoration movement.