Here's what's going to happen, because I've seen it before.
The government creates a big tree-planting program. A bunch of Wyoming ranchers who just happen to donate to politicians- just a coincidence!- will get paid millions of dollars, which they'll mostly pocket. But they'll buy some cheap non-native seedlings and wreck their native grass rangelands putting them in.
6 years later, during a drought, the whole thing burns, releasing all the carbon anyway.