https://en.wikipedia.org/wiki/Billion_Tree_Campaign
Looks like the UN handed the program to 'Plant for the Planet' (Germany) in 2011.
'https://www.plant-for-the-planet.org/en/home
It'd be fantastic to see this organized nationwide in the U.S. ... and promoted as part of the campaign.
P.S. This video, 'Planting Bare Root Trees With A Dibble', shows how very easy it can be to plant a seedling. Anyone can learn it in a short time.
https://www.youtube.com/watch?v=jhqa3yeLxhk