You voice your opinions where you can. Be it online or on the streets. I also think a big part of it is how you speak and use your words. Far to many people just scream and shout and say nasty things and wont listen to any other thoughts or opinions and wont have an open mind and then there are people who are willing to have a calm and open discussion. Also I think its very important when you have a discussion to base an opinion on facts and logic and reasoning and not just made up stuff.
Now to answer you question I don't think mega tech companies have as much hand in the government as you may believe. I remember a handful of accounts where some of the companies defied the us government and fought against them. Do the big tech companies as a whole represent the people in a way yes but that's the world we live in where we are represented by the majority not the minority. If 100 people say yes to something a 2 people say no should everyone go with the no just to make those 2 people happy?
Not every outlet is controlled by a huge corporation and if you aren't happy with how those corporations are handling things then you make you own platform. Its not the responsibility of a corporation to get your message out into the world its yours.
I hope I have answered your question but maybe not. One of the great things about living in the USA is that we are all free to have our own thoughts and opinions and have discussions. I could be wrong too and if other people think and feel differently than you or I they have every right to do so.