(And I can already feel the aneurysm I just gave half the people on this forum)
Subsidized higher education, universal healthcare, and higher taxes on the wealthiest are still all fine ideas, ideas I fully support. But the world needs less people regardless of those policies. We overshot global carrying capacity, and you can't socialized economic system your way out of that.
I agree socializing developed nations' economic systems isn't having a huge effect on the global population growth. Focusing on the real problem means investing in the health & development of those with the actual highest birthrates, not making U.S. colleges cheaper.
[0] https://wol.iza.org/uploads/articles/228/pdfs/female-educati...
I'll go so far as to say that empowering women through education and family planning access alone in some countries isn't enough; you might have to provide direct cash payments to assist in developing agency through career development or entrepreneurial efforts. Otherwise, from my research [2] [3], they're beholden to their partner's family wishes (which may not align with their own, and they may not have the safety or security to assert their will).
[1] https://ourworldindata.org/fertility-rates/
[2] https://theconversation.com/family-size-why-some-nigerian-me... ("Family size: why some Nigerian men want more children")
[3] https://www.scientificamerican.com/article/africa-s-populati... ("Men also have to relinquish sole control over the decision to have children and refrain from abusing wives or partners who seek birth control.")