This post (especially this section) explores this. There are also some ideas on this website. I’ve copied and pasted the ideas from that site below. I think it’s written with a more international perspective, but likely has some overlap with actions which could be taken by Americans.
Promoting free and fair elections, especially at the midterms
Several NGOs are well established as working on this, eg Common Cause works to reduce needless barriers to voting and stop gerrymandering, etc. Verified voting advocates for secure voting systems, and the Brennan Center for Justice researches and advocates for relevant policies.
Enabling bravery of key individuals.
Example: Mike Pence was very brave in standing up to Trump and enabling a transition of power, and he has been vilified for this by Trump and his supporters.
Today, members of Congress don’t always seem to stand up for what they believe in (eg not opposing controversial appointments such as RFK and Hegseth). Presumably they are concerned about threats made by Trump.
Unclear exactly what this intervention looks like (provide financial support? Or something else?)
Consumer power and investor power
The boycott of Tesla is an obvious example of this, and Musk is clearly feeling the pain.
Further work could identify and assess the extent to which other large corporates are kowtowing to the Trump administration, so that consumers can make informed choices.
People who are members of pension schemes could write to the trustees asking them to divest from relevant corporates (Tesla being the obvious choice at this stage, this large scheme has already divested from Tesla). Furthermore, people could coordinate this activity.
Support grassroots protests
MoveOn, Democracy forward, etc
Bail project
Supporting free and balanced media
We need media sources which are critical of government.
Such media sources don’t seem naturally set up to accept moderate sized donations. Paying them subscription fees can support them, although the amounts are modest.
Large donors could reach out to suggest an investment in their work to bring about more work which is critical of government.
Avoid travelling to the US
Reducing tourism revenue may have a (very modest) impact on the US.
Several countries have issued travel advisories about going to the US, so this may make sense for self-interest reasons anyway.
This is an important and valuable question, thank you for raising it. I’ll split my observations into two effects:
Malthusian effects
Benefits of scale
Malthusian effects
Other responses have referred to Malthusian effects, by which I mean the concern that with only finite resources, the resources will be spread between more people, and each person will have a worse quality of life.
Benefits of scale
Creating another person doesn’t only create another mouth to feed. It also creates another source of ideas and creativity.
For example, each new birth has the potential to become another Norman Borlaug (who is claimed to have saved a billion lives through his research).
Even if 999,999 new people fail to come up with a ground-breaking innovation which makes the world better, if the millionth person does, it could allow everyone to benefit.
Of course, the flipside is that any new person could be the next Hitler/Stalin/insert-your-favourite-bad-guy-here.
Are the Norman Borlaugs winning over the Hitlers?
If you believe the data that seem to suggest that the world has been getting better over recent centuries, the answer seems to be yes.
There’s also benefits around the fact that niche interests/needs are better accommodated at scale. If 0.01% of the population has a rare disease, and the population is 10 billion people, that’s a million sufferers—enough scale to incentivise scientific research. And if successful, maybe everyone is cured/treated. For a significantly smaller population that disease may remain untreated for a very long time.
Do the benefits of scale win over the Malthusian effects?
I don’t think this is obvious, but I’m inclined to think the benefits of scale win.
If we look at recent examples of challenges that humanity has faced, human ingenuity has managed a few good successes (the aforementioned example of Norman Borlaug and dwarf wheat; the cost effectiveness of solar power has improved dramatically in recent years; smallpox eradication; saving the ozone layer). Don’t get me wrong, we still have more to do! But that suggests we want more brains, not less.
Furthermore, decisions we make today should be based on how the benefits of scale will work in the future, not how they were in the past. Will we be better able to use our ingenuity to solve big problems in the future? Some would argue that AI will make us better able to explore creative new solutions (not that everyone will agree on this).
Lastly, and this isn’t really answering your question, but rather picking up on a comment of yours. You said that the idea that saving lives makes the world better is a “core assumption of the effective altruism movement”. I don’t think this is correct. EA is a movement built around using evidence and reason to do good. If the evidence showed that saving lives was bad, the essence of EA would be unchanged. Furthermore, lots of the practice would be unchanged too—a lot of EA activity is not linked to saving lives.