You can technically write whomever you want on your ballot. In most states. At least in PA where I live every slot on my mail in ballot had a write in box.
The problem is that there is no coordination of the people to actually change the status quo. Too many people are still content with it. From both sides movements like BLM, Antifa, Occupy, the Tea Party, the alt-right, etc represent at most a tenth of the nation. And by-and-large the other 80% not participating in political activism at all largely either A. don't believe in the ability to organize a movement for change or B. don't want it at all.
This is not to say it would not be in the self interest of a vast supermajority of Americans to seek such change - for example, universal public healthcare would be a tremendous boon to like 4 in 5 people at least. Better elections, with election day being a public holiday, universal mail in voting, and any of the myriad alternatives to first past the post voting would all improve the conditions of like 95% of the country. The problem is that most people were taught and conditioned to be non-participatory and largely will not become so no matter what anyone else does or says . Even if things did get bad. Even if there were tangible impacts to their day to day experience. Conditioning is an extremely potent force and a combination of American corporate news, American public education, the cultures of swathes of the country raise their kids on, the material conditions you live through and your life experiences within them, etc all contribute to the apathy and attitude.
Thankfully the dial is moving in a positive direction, I think. Anyone under the age of 40 to greater and greater degrees was unable to grow up in an isolated microcosm of Americana that conditioned them into non-participation. The numbers still aren't great, but they are getting better, and unless we see systems collapse take us all offline it will hopefully keep improving moving forward, albeit centralized private social media has done a lot last decade to stymie progress.