It's my belief that people will vote, Americans included, if they think it matters. In Denmark fewer than 80% vote for the EU parliament, because very few actually care, even though the EU have a huge influence on our laws, it's just not clear to the public. Similarly I find it more plausible that the average non-voting American simply don't believe voting will have any real impact, rather than choice to stay home because they don't can't spare an hour every two years.
There's a number of things I personally believe the US should do before looking into online voting, if the goal is increase voter turn out. Losing the "winner take all" system for one. Having more parties represented in the congress and senate could help people feeling that they're better represented and that their votes actually matter.
2. In Presidential elections, #1 holds true. But, even worse, due to the electoral college, some states have outsized influence on the outcome. Voters in CA have less voting power than voters in North Dakota. This is due to each state having a minimum number of electors, but a fixed total number.
3. Even ignoring #1 and #2, at the national level, there aren't big differences between the GOP and Dem positions on the things that will impact an average person's day to day life. Elections always come down to "those guys kill babies" or "those guys like to arrest black people". This is less true at the local level, where property taxes, schools, etc actually do impact daily life, but for whatever reason, those elections are less interesting to most people.
4. Voting in the US is during work hours; it is not a holiday. Hourly wage-earners are frequently forced to forgo income to vote. The GOP deliberately understaffs polling places where possible to increase wait times and make voting as tedious as possible. They also regularly attempt to stymy voting through ID programs, misinformation campaigns, intimidation, etc.
5. 24-7 news cycle has many people worn out and frustrated with the system. There is a growing sense of "fuck it, let the whole thing burn" on both sides of the aisle.
Also, if people are only voting once every 2 years, then they're still opting not to vote in a lot of elections (elections where there vote has a lot more impact).
[1] https://www.nytimes.com/2016/11/09/upshot/why-long-voting-li...
[1] https://www.nytimes.com/2016/09/17/us/some-republicans-ackno...
I think some people have a principled stance against voting. You may not agree with that but it is another reason why people may still not vote.
About one month before elections, or a referendum (ca. 3 times a year) you get a resealable envelope containing all voting materials.
You cast your votes and put the slips into a sealed envelope (which ensures confidentiality). Then you sign the voter eligibilty card (which also serves as the return address), stick it into the envelope in which you received the materials and drop it into the next letter box.
The materials are checked and the sealed envelopes are stored until voting day, when the votes are counted.
Inconvenience, even if you live out in the total sticks, is really no excuse for not voting in Switzerland.
Can the system be gamed? On a very small scale probably yes if you really, really want to and are really careful. Gaming it on a significant scale? i really don't see how.
Edited for clarity