How does not buying Jack Daniels in any way harm Trump? Now not only are you doing something that is, by your own admission, completely futile, but your futility is aimed at the wrong target.
Good grief, it has absolutely no effect at all. But if someone else said 'Hey, good idea. Let's set up an app whereby we can determine what goods are made in the US then we can release it for free. Stick it to the man!' does that in itself do anything? No, it doesn't. But say a few thousand people use it, will that make a difference? No, it will not.
But if you get a news station running a short segment on it and a local paper picks it up and then the nationals pick it up, it becomes news. The international papers might run it. So will that make a difference? Well, yeah. There's a gradual realisation that there is a degree of push back in the community. And that will spread. And that might, in some way, actually make a difference. A local politician might pick up on that and run with it. And there may be an election and she gets in partly based on her position.
You've seen what just happened in Canada. There was a backlash against Trump in that the conservatives took a hit. The same thing just happened last weekend in Australia. Our equivalent of the Republicans ran on some policies that could only be described as MAGA. They were thought to be the favourites to form a government. They were hammered. It was a landslide for Labor. And one newly formed party, backed by a local billionaire, farcically named 'Trumpet for Patriots' (gee, you'd never guess what sort of policies they ran on in regard to immigration, gay rights and climate change) were wiped out.
One small action, one vote will not make a difference in itself. But if no-one took that small action, if no-one cast that vote, then nothing would change. Your attitude seems to be that unless what you do specifically makes a difference in itself, then it's not worth doing.