The voting system amplifies the problem. In the American system it takes far less than 50% of the voters to take control of a party. And a voter dissatisfied with the options offered by the two largest parties have to either vote for the lesser of two evils or have no influence at all.

With better voting systems there is an opportunity for more political parties. The latest election in Denmark is an example of that with 12 different political parties represented in the parliament. Moreover the Danish system also has a tendency to make members in the center of the political spectrum have more influence than an equivalent number of votes on the outer wings. A center party with only 7.8% of the seats played a major role in the government negotiations much to the annoyance of a far right party with 8.9% of the seats.

There are many other countries with better voting systems than america. For example there are countries with two round presidential elections where the top two candidates from the first round go to a second round. This means voters are free to vote for their preferred candidate in the first round without risk of having no influence. In such a system there is a very real possibility that enough voters dissatisfied with the two mainstream options can vote for a third candidate and displace one of the mainstream candidates in the second round.