There's not much that any one of us can do alone. Refusing to make excuses for an unjust system, and finding ways to make the shitty bargains required for survival that at least minimize the extent to which we support it, is the best sort of start I can suggest. We may be forced by circumstance, especially those of us who have given hostages to fortune, to be complicit. But we can recover some agency at least over the extent of that complicity.
I'd like to be able to suggest some group or movement here, but I've never been much of a joiner. The BLM folks I've heard from seem to have good heads on their shoulders, though. You could do a lot worse than to consider their suggestions on the question of "how do I help?"
I definitely do understand feeling powerless. But remember also that, as a middle-class white person, especially if you're male and the head of a conventional family household, that puts you pretty close to America's own idea of what America is. Believe it or not, there's a subtle kind of power in that. Things that might likely be ignored when said by - oh, someone like me, for example, who while also middle-class-ish white is a weird queer redneck loner and always has been - often are taken more seriously when said by someone who presents a gestalt of commonplace American normalcy, simply because of the sort of person who's saying them.
That really is a power all its own. If your social and professional circles are anything like mine, you can often enough find opportunities there to wield that power - gently, of course, and with real care for those with whom you're talking; to be, or to be seen as, a humorless woke thought editor, is to fail - in a way that might help redress injustice in a small way simply by convincing someone else to think about whether they should see the world a little differently from how they have before.
It's a small thing, for sure. And it can on occasion be a risk; if nothing else, to speak honestly from the heart on any subject constitutes a degree of vulnerability, and people don't always treat that kindly. But little in my experience worth doing is entirely unattended by risk, and little in my experience does more to ameliorate a sense of powerlessness than to hear someone say "you've given me a lot to think about", and then to see over time that they have thought about it.
It's subtle, as I said. It's a small thing, and it doesn't always work. But it is something. And even when you fail - which you will, sometimes at least - at least you will have tried, and even in that there's a kind of consolation to be found.