"Candidates compete for a single seat, and just fifty percent plus one vote is all it takes to win."
Most states utilize plurality voting which does not require a majority to award a winner. California and Washington implemented top two open primaries -which I oppose - that ensure that the winner of the general election will have a majority unless there is a tie vote. Ranked choice voting - which I endorse - implemented by Maine and now Alaska ensure the winner has a majority of the total votes cast.
"Talking about voter power, we can state that our voting system is based on a competitive mechanism that leaves a large number of voters unrepresented, and yet no one seems to be bothered by that. To make it worse, this point is hardly ever debated, it is quickly pushed under the rug."
The duopoly relies on plurality voting to perpetuate their major status.
"First off, a political dark horse may end up spoiling the race between the two usual candidates, becoming the unexpected winner."
I disagree. Instead, what happens with plurality voting is a vote cast for a third party or independent candidate helps the least desired major party candidate win.
"All voters (99.9 percent) get the candidate or party they hand-picked themselves in nations with proportional voting."
I agree if there is a large number of representatives or the party votes are a significant percent of the total votes cast. The best performing Green Party candidate for U.S. Senate in 2020 was Lisa Savage with 3% of the total votes cast. Most Green Party state U.S. Representative candidates received around 2% or less of the total votes cast. Even for California with 53 representatives 2% of the vote would not qualify for one seat. Libertarian Gene Siadek received 6.4% of the vote in the Nebraska US Senate race against a Democrat and the Republican incumbent. This is only the third time since 2012 an LP candidate has picked up at least 6% in a US Senate race.
"The US Constitution as it exists today requires full proportional voting for cities and counties."
Please cite Article and Section.
"Become a member of the Green Party or the Libertarian Party and drag them toward supporting electoral change; they are now failing the voters for not (yet) embracing electoral change."
The Green Party platform approved on July 2020 promotes "proportional representation voting systems for legislative seats on municipal, county, state and federal levels." and "Ranked Choice Voting for chief executive offices like mayor, governor and president and other single-seat elections." The 2020 Libertarian Party platform supports "election systems that are more representative of the electorate at the federal, state, and local levels. . . oppose laws that effectively exclude alternative candidates and parties . . ." This month the South Carolina Libertarian Party is launching a campaign to replace South Carolina plurality general elections with ranked choice voting general elections.