Good reply, Bob.
Of course, I have to disagree, while I do agree with your arguments as they exist in their natural context.
In our world, there are hardly any nations that have the pure proportional voting system, and as far as large nations go that may be just as well for the better (as the article points out, too).
Yet, we have a hierarchy of power in the world of nations, and the USA sits in top position. One of the reasons the USA sits in top position is not its size per se. It is creating good conditions in which the elite gets a lot of the profit. Or, talking with power in mind, the elite can keep on doing what it is doing, less bothered about sharing their power.
The USA being a two-party nation affects the world negatively -- but not the elites of the world that like to invest in the USA; they benefit. Their foreign investments in the US will reap them greater rewards than investing in nations with proportional elections or nations with more than two parties that share with their entire nations instead of just with the elites.
So, the top dog of power becoming a three-to-five party system will benefit not just the people of the United States but the entire world. It will lower the reality in which competition is put in place for nothing other than competition. There is nothing wrong with competition, but when all compete for the sake of competing then a lot of money and energy is wasted on that nonsense competition for no good reason (other than benefiting the elite or creating a side-show that pulls attention away from the actual center of power).
Competition should be about making societies the best they can be.
The result? Proportional voting are winning this competition with ease.
Only when those that need a decent minimum wage end up receiving representation that can make their minimum wage be a living wage, only then do we live in a decent nation. Today, in the USA, we do not have a decent voting system because those dependent on minimum wages are not represented in their natural numbers. They are tremendously underrepresented. The minimum wage in the USA is not a living wage.
Lastly, once more, the gini index of the world. Follow the link and see with the first global map that the United States is the worst nation of all rich nations in the world, not sharing their wealth with the bottom of society.
https://en.wikipedia.org/wiki/Gini_coefficient
Any other discussion is freewheeling in the air. We need to discuss the voting system and what it delivers. In the United States that is not all that much. Our politicians love to sit on their hands. They kick the can down the street and they leave minimum wage at an indecent low level, all for the sake of attracting foreign investors (and our investors loving it here, too).
Yes, always good to have a decent discussion on systems and outcomes. Thank you, sir.