The USGS rapid assessment report (the link above is to the Science Daily article summarizing the USGS report) shows that most of the estimated additional forest biomass carbon sequestration capacity is accrued in areas currently occupied by agriculture and development. Beyond the scope of the report is the question of what kind of economic pressure would force a reduction in agriculture acreage to free it for replacement in forests.
There's only one change I can think of and that is change in the American diet to one consuming less animal products. Food-animal production consumes the greatest total amounts of land, fertilizer, pesticides, and water and is not only environmentally unsustainable but also irrational in terms of energy use.
Even algae-farm protein and fertilizer production, if the bulk goes into cattle production, would still be highly inefficient and unsustainable due to the extensive land needed for forage production. Forage production requires huge amounts of land, fertilizer, and water.
There is no foreseeable government action that would require Americans and others to modify diets away from a meat-centered one. Diet and transportation constitute a huge portion of an individual's environmental footprint. Eating less meat would free up land for forests, thus enabling greater carbon sequestration.
The USGS has laid the groundwork to show us it is possible that greater carbon sequestration can occur all around us. But, only you and I can elevate the maps and calculations to reality. It all begins at the dinner table (or fast-food drive-in lane).