Personally I think mandatory voting is a bad idea. It will not make then suddenly care, they will just vote for lolrolfcopter party.

The US does a lot of bad things around voting, but it being on a workday is probably the biggest hurdle. Most other countries have it on a weekend or holiday. That means that most people can go vote and not have to chose between potentially getting fired and vote. Which, to no surprise mostly affects lower income voters.

Also combined with the witch hunt on mail in voting makes it very hard for lower income people to vote. Which is by design.