Meaningful legislation follows collective individual conviction - this mindset that the individual does not matter is simply an excuse to resist change, which means that government will basically never feel the mandate to make any meaningful legislation. People must be willing to be better, and that starts with personal investment in the problem. For example, if you bike more and use transit more, even when it is mildly inconvenient, local politicians and authorities are far more likely to invest in those modes.

Further, there is a lot that people can do to their effective emissions, regardless of external emissions. Quitting meat, for example, is an individual action that can have enormous benefits collectively. Buying solar panels and home investments, even at a slight loss, drastically reduce emissions. When you talk about externalized emissions, you fail to admit that a massive portion of the global emissions are due to the individual consumption of resources. Period.

Additionally, individual political action - donating, campaigning, and running, are all individual actions that contribute to the greater collective action. The idea that this is fundamentally different than other type of individual action is wrong.

As far as I am concerned, the mindset that the individual doesn't matter is an immensely toxic and dangerous one: it is escapism, denial, and a transparent effort to assuage one's personal guilt toward responsibility.