Ok. If you don't? There's still countless aspects of your life that you interact through the economy to fulfill that have the potential for change and improvement.

Still buy new clothes from Old Navy or JCPenney? Maybe think about going to your nearest GoodWill or local thrift shop(s) (and on a regular basis) to see what gems pass by now and again. College towns right after the end of the semester are ripe for this, and I would wager that you have a college town somewhat closer to you than any kind of public transit. Not saying that you have to do this for your entire wardrobe, but choosing used over new means that resources are avoided in making that new garment, such as all of the fuels needed to move resources to and from each factory along the value chain, all of the solid waste destined for landfill or incineration from the scraps of cutting-and-sewing that new garment, all of the water pollution associated with dyeing or printing your new garment, or the potential human rights violations that could pop up throughout the value chain. A lot of these can be mitigated by buying more sustainable brands that seek to minimize these things, but a cheaper alternative is to buy used too.

Still have an air conditioner? Maybe think about hooking up a smart thermostat or equivalent and enrolling in peak-load demand response initiatives so that your AC or furnace works a little less hard in exchange for the entire grid not having to provide as much power (the alternative is blackouts or brownouts where everyone turns their AC on blast but kills the grid so no one has power anymore). Doing this means that demand curves by customers don't reach as high of historical peaks, which allows utilities to avoid using peak response assets like Combined Cycle Combustion Plants that use natural gas to operate. You in turn create a greener grid, that's also better for the climate. And if having a warmer house isn't enough for you, there are other ways of mitigating this, like setting up phase-changers directly to your bedroom so that it stays cool, unlike the rest of the house, or buying ice vests that you can wear on your person, or going to a public facility like a library or mall and centralizing cooling loads to there instead of decentralized cooling loads via everyone's homes.

How old are your assets like cars, AC units, furnaces, fridges, etc.? Perhaps if it doesn't break the bank, look into purchasing models that are more efficient, as in those cars that have better mileage and/or that are hybrids and can be plugged in to a normal outlet to charge, or fridges and AC units that use coolants better and that have better insulation to keep things cooler for longer. These choices don't necessarily have to be accompanied by the insane bits of technology and information that bigger companies want to shove down our throats with these newer, smarter devices.

Does your local grocery store carry organic goods as opposed to conventional ones? I know that ALDI near me carry those, and I've had to shop there for years thanks to the low prices they offer. If you minimize your costs while still going organic, maybe consider shifting your diet away from red meat and pork towards other options like chicken, fish, or straight up whole food, plant-based ingredients like vegetables, fruit, legumes, grains, nuts, seeds, mushrooms, etc. Or, if you've gone that far, have you considered seeking out local farmer's markets near you that often offer these goods both organically (or "organically" since the official label is so expensive), in season, AND locally. A good resource for finding farmer's markets near you is https://www.localharvest.org/.

Getting back to the public transit problem you bring up:

Is there public transit near you? Do you know for sure? Most major cities like Houston, Chicago, New York, San Francisco, Los Angeles, and even the smaller ones like Cleveland, Oklahoma City, Las Vegas, etc. do have some version of public transit, whether that's via subway, rail, tram, or bus, so perhaps there are more options near you thank you might think. And do you use these when you have the opportunity to? All of these services are offered via companies that use metrics like ridership and rider time to gauge how they might want to invest in these services into the future. If you start engaging with more and more public transit when you can, every human adds up on their balance sheets and can impact what happens with public transit in the future. I know that in my area, the public transit corp running our interurban train is constructing a new service line South, when it traditionally only extended East & West, which will capture an even larger portion of the market and make the service even more financially lucrative over time, leading to even more expansion and coverage. But I do agree with you on the lack of other interurban solutions like Amtrak. That service is downright terrible, and we as a country (assuming you live in the US) need to start demanding better service, as well as less of a grip on the railway network in this country by the railroad tycoons.

There are changes that can be made all around us that involve the economy and a corporation on the other side. All of the above examples I listed do. There are two sides to the economy, that economists tell us: Supply and Demand. Just because we can't control supply outside of efforts like political action doesn't mean we can't control demand too. Little changes that every common person makes over time one way or another add up and show up on these corporations' balance sheets.

Hope is not lost. Stay focused on sustainability and making what changes you can make in your life right now and into the future, including political action. All of this adds up.