I came across the issue of litter twice: in both a city planning and a behavioral economics context. It is however, much more of a behavioral psychology or marketing question, so someone with more experience in those two fields may be able to comment more in depth.
The short answer is that, while pop history credits Lady Bird Johnson with single-handedly "making America clean again" (not a direct quote), it's more accurate to give credit to the "Keep America Beautiful" (KAB) organization. This isn't to discredit Lady Bird, who definitely helped publicize the issue, and was definitely instrumental in passing the Highway Beautification Act of 1965 which played a role in making beautification - and therefor littering - into a topic of national discussion.
KAB was founded in the early 1950's by the Ad Council and it continues to operate to the present day. It has a very helpful history page with a timeline. Some more extreme environmental outfits assert that it was founded by corporations (which is true) to preempt national anti-littering regulations that would be costly to big business. My personal opinion is that, if this even was the case, the corporations did a damn fine job and we definitely don't litter as much anymore. KAB did a serious of advertising campaigns, with the most memorable being the "Crying Indian" ad in 1970. (For context, given that you're coming from the UK, Native American issue were a big deal in the early 1970's, with Native American activists seizing the prison island of Alcatraz from 1969-1971, and Marlon Brando sending Native American actress and activist Sacheen Littlefeather to refuse his Oscar for the Godfather in 1973.)
By 1972 the study of littering was starting to enter the academic discourse. The study, as more recent studies continue to, drew heavily on KAB research and focuses on the cost of cleanup as well as the negative aesthetic impact.
TLDR, the success of the anti-littering campaign was due to a long-running advertising campaign and the high-profile impetus provided by Lady Bird Johnson, eventually pushed Americans to see littering as a costly and ugly social ill. For an in-depth analysis of how the marketing worked, I hope a "marketing historian" can answer that question.
I don't have any specific knowledge of the experience of the UK, but given your question I looked into it. I'm so glad that I did, because Britain took what America was doing with Keep America Beautiful and made it so much more charming with Keep Britain Tidy. It's the same general idea - an advertising focused effort funded by private industry and promoted by celebrities - but with a mascot named "Tidyman" and a campaign called "Clean for the Queen". So thanks for that.
Hi, friends,
Welcome to AskHistorians! This is a subreddit where people with questions about history can get answers from those with expert-level knowledge in the field. We ask that all posts be in-depth, comprehensive, and supported by current academic research. We do not allow answers based on "Source: I/my mother/my teacher remember(s)..."
Because it can often take time for someone to write an answer, you may well see this thread from your front page or r/all first. Please take the topic to heart and do not litter the page with complaints and answers that break our rules.
If you are interested in the answer when it gets posted, you can send a PM to /u/RemindMeBot with the link to the thread in brackets and the time frame when you wish to be reminded.
Finally, if you just want to read some great history, our Sunday Digest links many of the best posts each week. And our year-end link assembly of people's favorite posts can be found here.
Thanks and happy New Year!