Irespective of your own party-political views, that such a large proportion of the electorate abstained would be a serious matter in any democratic country.
There are two ways a voter can undermine the system: abstention (not bothering, or refusing, to vote, or annulling the ballot slip), or so-called "tactical voting" (dishonest).
Some countries, including Australia, make voting compulsory, but they might have an "Abstain" choice on the ballot slip.
Some people in the UK, where voting is voluntary, call for a box marked "None of the above", but really, if you cannot comphrehend a two syllable word like "Abstain" so need four monosyllables, what hope have you of comprending political debate in any sensible way?
"Tactical voting" , also called "Protest voting", applies to systems fielding at least three parties, so might be virtually non-existent in the USA - though I may be wrong there. It means that rather than voting for the party you support sincerely; you vote for another in the hope of making the third lose. So voting dishonestly, certainly not by sincerely-held principles.
Both abstaining and dishonest voting are bad for a democracy, and a refusal as high as a third is serious damage, whoever wins. It risks a close result not fairly representing the citizenship as a whole; but the non-voters have only themselves to blame.
I do not advocate compulsory voting even with an "Abstain" choice; but I do hope people do take their right to vote for their choice of party, as also their responsibility.
I have no time for "makes no difference", "can't be bothered", "they [politicians] are all the same" ["same" as what or whom?] and similar lazy excuses for not even thinking. Nor for those who complain about, or even indeed welcome, the result but admit having not voted.
Irrespective of their nation and its parties, such people are un-, or even anti- democratic.
.....
The above of course applies in democracies. Dictatorships do have elections but are shams made to return foregone results for the premier or party in charge. There, it would not matter if no-one votes. Many Iranians did not vote in their last general-election, so predictably perhaps the regime blamed it on foreign propaganda, not on a few, simple home truths about itself.
