I’m not sure how much understanding the issues is a factor in democracy functioning well. I think it has more to do with widespread belief in democratic and rule-of-law identity, such that voters will reliably punish those who violate those tenets, and structures set up to resist the kind of rot that targets inherent weaknesses in democracy, especially to prevent capture of media and lobbying by rich minority interests. These reduce the effects of directed exploitation of voter ignorance, and block democratic attacks on democracy itself.

Both of those factors are, to use the scientific term, completely fucked in the US, which is why we’re where we are now. We’re not here because people think that we spend 20% of our budget on foreign aid, but rather, people think that because of concentration and capture of media ownership, and intense lobbying. The ignorance would be there either way, but the direction and form of it is carefully cultivated, and allowing that cultivation is the problem.

The generation of hard data demonstrating that voters (more or less) don’t know jack-shit about anything goes back to IIRC the 1950s, and the best answer Poli Sci has for why this results in a functioning system at all is that voter behavior is fairly erratic (much of it amounts to “do I perceive that things are bad, even that have nothing to do with the government or with me? Then throw the bums out!”) and (this was once accepted but is now controversial) that voter ignorance kinda balances out by virtue of being chaotic. If that ignorance becomes directed, however, both of these things are weaponizable or breakable.