However, you may be able to use programs like Blackrock's Voting Choice to gain a limited amount of voting power from ETF shares held in your 401(k) or Roth; this seems to be an easy option to exert some influence at practically no cost (other than investing in your retirement).
Unfortunately, you are forced to select from a list of general strategies; you can't vote on individual proposals, nor create proposals. Since basically no fund has a AI-safety-focused voting strategy, you would probably just set your fund to the ESG, SRI, or sustainability-focused strategy, as these voting strategies probably have the most alignment with AI-safety concerns (which is to say, more than zero).

Edit: o3 also suggests using a direct indexing SMA mirroring whatever ETFs you are using; this would allow you to gain direct authority over what proposals you are voting for/against, though with increased fees (and obviously, much more mental effort required).

Edit 2: Another idea: if you are employed at these companies, instead of just waiting to vest your RSUs, you could probably just use what stocks you gain to send and vote for AI-safety-focused proposals (maybe also selling at a later date). Obviously this would require the RSUs to give voting-class stocks, though.

Yes