More babies would certainly help but only in the long run. It may be literally impossible for the government to get women to have more babies, anyway. Fertility is a deep cultural thing which may be beyond any incentives the government can provide. Even if you can figure out a way to increase fertility it would be at least a couple of decades before it would help.
In any case, more babies isn't the only solution. The other solution is increased immigration. That gives an immediate increase in the working age population. Also, for literally centuries, the U.S. economy has been invigorated by the contributions of immigrants. They're good for the U.S. The problem with increased immigration is that those who most want to immigrate to the U.S. tend to be black or brown which enrages a significant portion of the existing population.