For the host of reasons listed in other comments (and others too), it will never pass that everyone plants a giant sequoia. This means the “ideal” proposed solution is not possible.

Therefore, why not aim for a more realistic goal: 1. plant trees in vacant spaces (such as highway medians), any kind of tree 2. Plant 1 extra tree instead of more lawn in your yard.

I’d guess these goals are more attainable and though would not offer a full solution, would be better than no option.