There are a few big reasons for what the author is observing and commenting on, that get too little attention IMO.
One is the end of the cold war, and the wars preceding it. The cold war was cold, but the psychology was regular war psychology. Fear, demonisation, rallying around your side... Relative evaluation of conduct and goals, rather than idealistic evaluation.
In the corld-war-world, the US represented democracy, personal liberty and its associated human rights, and (very importantly) culturally icons. US and western police forces behaved well relative to Soviet police forces. US Movies & Music were better. Press was more honest. The comparison was not made relative to an idealised concept of democracy or human rights (or music). It was made relative to the Soviet Union associated states. It was also mostly made in Eastern Europe, where the divide was arbitrary, non-national and highly visible.
That dichotomy world is gone. These days, I think people evaluate these things in a more abstract way, relative to abstract idealizations.
A second effect is US politics' global viewership. This is a product of globalized media, the dramatic merits of US political theater, the genuine impacts of big US decisions and other reasons.
This is huge. I live in Ireland. The majority of people are more knowledgeable, vested and opinionated about US politics than local politics. They have a strong opinion on US health policies, but not Irish ones. This is a recipe for insanity. US politicians are pandering to US opinions, not Danish or Georgian or Irish opinions. Of course they feel unrepresented. When one side loses a heated election, large numbers always feel alienated and angry at the country. It passes, a normal part of democracy. Many Danes (and everyone) were involved enough emotionally to get the same feeling but being non-americans aren't as affected by the normalizing effects that bring everything together in the end.
When Europeans express a frustrated criticism of US politics, they are doing it as insiders. They are criticising it the same way they would criticize a local party coming to power, one which they don't like. Imagine how angry Americans would get at the Danish or Mexican parliament if they were following it like this.
A third issue is the "someone must be driving" fallacy. In this sense being angry at the US is like the constant anger at one's own government. There is so much wrong with everything and it has to be someone's fault.
The US has been having a bad run in foreign policy. Afghanistan, Iraq, Libya, Syria, even N. Korea, ... The US is (rightly or wrongly) held responsible as the guy in charge. Politics rarely rewards successes. The failures are just more visible.
Who do you get angry at for the Syrian civil war? Who's to blame? The UN?