It's like voting. No, my individual vote doesn't matter. But thousands of individuals voting can. Luckily, you are not alone in efforts to help reduce our impact, so it does add up across the population level if people do try to reduce their impact.
At least in the US, voting is also meaningless due to things like the electoral college.
That depends on whether one lives in a politically diverse state.
In other words, if you want your vote to count, you need to live where it counts.
Personal actions on this sort of issue are meaningless and always have been.