Set up a recurring donation to ProPublica. They have been a thorn in the side of those shitheads at the supreme court and we need their investigations in a Trump presidency now more than ever. https://give.propublica.org/give/346423/#!%2Fdonation%2Fcheckout%3Fc_src=UpRed
You could also try to get in contact with a more left-wing group like Democratic socialists or something and get involved in letter writing campaigns.
Finally, get involved in a local issue - think city or county. Those meetings are filled with 1)people who have something to gain - developers, 2) retired people who mostly miss the point, and a few outgunned non-profits. You can make a really big difference.
He’s gonna do some shit again. Just have to wait.