This weekend, the streets of America were once again clogged with protesters as people marched in opposition to the administration’s detention of migrant children. A few days earlier, more than 600 women were arrested on Capitol Hill during a protest against family separation — a protest organised by the leaders of the Women’s March, which brought a record number of American women to the streets last year to protest against Donald Trump’s inauguration.

A year and a half into Trump’s presidency, his opposition is digging in — as is the administration. Does this mean America is entering an era of permanent protest?

If it is, that era started well before Trump appeared on the scene. Most of the 21st century has been marked by mass protests in America, from the 1999 protests against the World Trade Organisation to the massive marches against the Iraq War to the emergence of the Tea Party and Occupy Wall Street. Time and again, frustration has driven Americans to pick up a placard and take to the streets.

Frustration is central to understanding why these protests have flourished. It’s not just disappointment with a lost election. Instead, it’s a sense that the political system is not effectively representing the popular will. And that’s something that has been increasingly true in the United States as both economic and political inequity have grown.

Take the Iraq War protests. Despite significant opposition, especially but not exclusively on the left, the authorisation of military force passed with 40 per cent Democratic support in the House and 60 per cent Democratic support in the Senate (and almost unanimous support from Republicans). The Congress was far more hawkish than the public itself, which, even after being misled by the Bush administration on the casus belli, nonetheless only offered a bare majority of support for invasion at the time of the vote.