I know few marketing execs would understand this these days, but I truly think that this would have been an excellent example of the time when having the Wonderful World of Disney back on the air would have been helpful (or even a special). You see, Walt Disney himself regularly used the weekly show to showcase their movie projects, and sometimes the parks, while offering a program (sometimes a drama, sometimes something about science or other thing). In this case, I think a good buildup like that (a modern show about Tomorrowland and Walt's historic interest in futurism, and about the innovations he and the imagineers put into the 1964 World's Fair) would have done wonders to set up the movie and to continue the narrative of Disney's heritage of mixing entertainment with education and forward-thinking.
They even did this with the World's Fair itself. The episode called, "Disneyland Goes to the World's Fair," is a great example of why this program mattered, both as entertainment and as a marketing tool.
The series was a stroke of genius that helped build up Disney's name in a lot of long-lasting ways, while still providing some entertainment value. It really helped us look to the world with wonder. It had the same viewpoint that Tomorrowland the film longs for. And, ironically, it would have been useful to set up the film if it were on today.
And even a TV special could have done the same. All better than the standard guest shots on Jimmy Fallon.
On a separate issue, I do wish that the movie had spent just a little more time in the setup, at Frank's childhood home and in the World's Fair. I do wonder if a lot of it were filmed but it just got too long, and they had to cut a significant amount of stuff. It feels that way.
Disney actually DID do this....but only in the Theme Parks as part of the pre-show for the currently running 'Tomrorowland Preview'.
At Disneyland, the 'Tomorrowland Preview' going on at the Magic Eye Theatre has a 18 minute pre-show that plays pretty much like you describe.
They even cut in some segments of this very program you shared...with Uncle Walt taking us through his latest projects at that time ( CoP was focused on ).
It was a well done short introduction to Walt's attitude towards pushing the boundaries and touching on his interest in futuristic concepts.
I can only assume the same pre-show is running at EPCOT's showing.
It would have been a nice piece of promotional material if it was extended to show as a short television special , or more probable for today's times, via YouTube/social media.
Instead of just releasing the trailers...which in itself seemed to cause some confusion in potential viewers, put together a 'mock special' similar to the pre-show used above and show some of this fabulous footage to the masses
A nice way to introduce a little background to the 'Walt connection'.
Regarding the Worlds Fair scenes, and how it seemed there could have been more of a set up to young Frank's beginnings there....well, there were other scenes filmed.
An entire segment was filmed at WDW's 'Carousel of Progress' for the film that was entirely cut out.
Who knows what other gems were discarded to the cutting room floor.
The brief scene where we see of young Frank at home working on his jetpack, being heavily discouraged by his Dad, could have been just one of several scenes shot in that setting.
Personally, i think in this case it was good to not focus too much on what was obviously not a happy relationship with his Dad since the film at that stage was all about a great big beautiful tomorrow.
The brief chip, in this case, hits the spot well.
Some fans of the film are hoping for a 'Directors Cut', but i am not sure if that will actually happen at this point.
I heard today people saying 'Tomorrowland's perceived 'box offic failure' is the reason why 'Tron 3' was killed off recently.
Just rumours and fan talk....but if it's true that is just a shame.