Agree to disagree. I've met enough Americans to believe that if we made voting mandatory, we'd just end up with Optimus Prime at the top of the ticket.
You can make an act compulsory on the whole population but you can't legislate duty-of-care upon the whole population.
Voting should be mandatory but the first listed option for every office should be "I approve of no candidate and think none of them should win" (the disaffected vote), and the second listed option should be "I approve of every candidate and don't care who wins" (the apathetic vote). With our current system it's impossible to tease out how many voters are disaffected vs apathetic vs simply disenfranchised (in the above scheme, those who don't make it to the polls at all), which makes it impossible to confirm or deny that any candidate has the mandate of the people.
Technically those options are trivial with a non-defective system like approval voting, but assuming you're stuck with first-past-the-post, that's pretty much correct.
Not quite, even with normal approval voting there's no way to distinguish between voters who want to say "all these options are undesirable and everything is broken" and those who want to say "life is good, I'm cool with whoever" and those whose votes get lost or obstructed. The reason why the notion of a "protest vote" is so pointless under our current system is specifically due to the indistinguishability of the first from the latter ("people didn't stay home because they didn't like the candidates, they stayed home because they're so content!"). Additionally without mandatory voting it's difficult to determine where and how voter disenfranchisement is happening, but at the same time it would be unethical to force someone to cast a vote without giving them the option to voice discontent with the options.
What definition of "approval voting" are you using? I'm talking about a ballot where each candidate is marked "approve" or "reject". With that system, "all these options are undesirable and everything is broken" is reject-all, while "life is good, I'm cool with whoever" is approve-all (and lost or obstructed is obviously no ballot at all; there's not much you can do about that).
