Brexit has created many nightmares, but a particularly unpleasant one is the rise of anti-English sentiment in Ireland. British-Irish relations have not just cooled on a diplomatic and political level, but among the Irish population. The anti-Englishness born of past oppression had, we thought, been confined to the past but has resurfaced. And whose fault is that? The emotional trauma of Ireland’s treatment by Britain, and England in particular, is usually delicately contained but now it is spilling over.

I grew up in Dublin, far removed from the conflict north of the border but I went to an Irish-speaking secondary school, where boys wore balaclavas to school Gaelic football matches for a laugh, and “IRA” was carved into desks with maths compasses. As the painful peace process concluded, and the Good Friday agreement came into force, God Save the Queen was sung in Croke Park, the hallowed ground of Gaelic sports, and the Queen spoke in Irish at a state dinner in Dublin Castle. It seemed as if anti-British sentiment was at least covered over with a healing gauze if not completely healed. But Brexit, and the behaviour and rhetoric of British politicians, the tone of the trightwing British press, and the constant stream of ignorance about our island from across the Irish Sea, has ripped that bandage off. Everything is exposed now, and it’s a wound that has been, and can be again, mortal.

“The English are at it again.” “The state of the Brits.” These are daily articulations of frustration from Irish people. Being hostile to our neighbours was briefly taboo among Irish liberals. But the Irish capacity to grit our teeth has turned into a daily grind.

Every clanger from a British politician – Karen Bradley’s offensive and ignorant statement exonerating British soldiers for their crimes in Northern Ireland; the border mess, exacerbated by the Conservative government’s tactical alliance with the DUP; the clueless remarks emanating from the House of Commons – has not just confirmed, but elevated our suspicions that English (and Brexit was always about Englishness, not Britishness, nor the oxymoron that is now the “United” Kingdom) apathy, ignorance and entitlement towards Ireland is as dominant as ever. The tactic of trying to undermine Ireland in a game of chicken with the European Union has also led to an existential fear that the EU will sell Ireland out, and a fury about the corner we are being put in.

With every bungled stage of Brexit, there is a dismayed head-shake about the fact that this is the first century where all of Ireland isn’t under British rule, yet still Britain finds a way to screw us. When Britain sneezes, we catch the cold.

How many working hours have been wasted dealing with Britain’s mess? How many millions has the Irish civil service across all government departments spent preparing for Brexit? How much time has been spent by politicians and civil servants negotiating and planning and troubleshooting? How much time and money has been spent across our agricultural sector, our industry, our hauliers, our universities, our arts and culture infrastructure, our small and medium enterprises, our ports, our police?

Ignorance towards Ireland is not merely the preserve of the Jacob Rees-Moggs and the Karen Bradleys. Surely every Irish person in England has stories about being patronised because of their nationality. One begins to wonder if all that healing was one-sided. Where was the soul-searching and the self-education on the British side?

It has also been difficult for the voices of the millions of British people understandably distraught by Brexit to cut through in Ireland, primarily because the hysterical conservative British press has drowned them out. But for every Brexiteer, there is a “well-meaning” English person who doesn’t have a handle on the basic geography and history of their island neighbours.

Brexit is also happening at a time when the first polyethnic Irish generation is coming of age. This generation has both formed and been moulded by an era of progressive social change in Ireland, where the LGBT rights movement and feminist grassroots activism have changed the political and social landscape. This is a generation that has taken responsibility for its future and stepped up to its civic duty. “Why didn’t they canvass?” is something I’ve heard said a lot by Irish people about those who voted remain and are now devastated.

This is the first modern Irish generation that is unselfconsciously patriotic, embracing a benign yet passionate cultural nationalism that is nonsectarian. The parameters of Irish identity are both expanding and spongelike; reaching beyond cliches, but also soaking up cultural attributes that were often deemed unfashionable by previous generations, such as traditional music, which has seen a resurgence, embracing regional accents in the arts, and reconnecting with the Irish language. But this confluence also offers a new generation an old enemy.

While pro-Brexit sentiment is, for many people, a jingoistic, colonialist throwback, anti-English sentiment is a familiar groove to slip back into. Neither is helpful, but right now both are very real.

• Una Mullally is a columnist for the Irish Times