That expected $100 - $1,500,000 is going to get spread around to 300 million people...

If you're so concerned with helping other people, why not just abstain from voting, thereby increasing the effectiveness of the votes cast by those other people, and thus giving them more direct say about how they are governed?

I actually also think your estimate of 55% belief is overconfident, for any utility function that properly distinguishes between terminal and instrumental values (i.e. a utility function that takes into account aggregate health is proper, while one that specifically refers to people having health insurance would not be in my view).