Fionnula Flanagan, the veteran Irish actor, has been a star of stage and screen for more than six decades, earning Tony nominations for her theatre work, a nod from the Screen Actors Guild for Waking Ned, a Saturn award for The Others and a voice acting trophy for Song of the Sea – as well as accolades for the cult TV series Lost.

This means she has spent a lot of time in the US – in fact, she’s lived there since 1968. The home she shared in the Hollywood Hills with her late husband, Garrett O’Connor, was well known for its parties – despite O’Connor, an eminent psychiatrist, being the first president of the Betty Ford Institute.

But Flanagan has fallen out of love with the US. She’s hanging out in Ireland and intends to sell up in Los Angeles after more than 50 years, a new McCarthyism is brewing and “hooligans” have taken charge of the White House, she says. The country is not doing well, she thinks. When her husband was working, alcohol was the chief vice. Today, “the whole of America is now so drug-ridden”.

When will she return, I ask, as she sits in an elegant hotel reception room in her native Dublin. Her answer is firm and succinct: “If I can fix it, never.”

Now 83, Flanagan is in town to promote Four Mothers, a tender comedy about a middle-aged gay author landed with the care of four elderly women over one chaotic weekend. Inspired by Gianni Di Gregorio’s delightful 2009 Italian comedy Mid-August Lunch, she stars as the leading man’s mother, Alma, who can’t speak after suffering a stroke.

For all the silence the role demanded, Flanagan delivers a tremendous performance as the matriarch of the overcrowded house, using facial movements and short, snappy instructions to her son tapped out on her tablet. The film is getting good notices, but Flanagan found it a challenge to shoot. “I don’t think I’ll do that again,” she says. “I really missed having my voice available. I’ve never done a role where I didn’t have the use of my main instrument.” Because of her roots on stage and in radio, she says, “I value my voice, and the temptation to use it was so strong. I had to just bite my tongue.”

The experience left her with a feeling of “enormous sympathy for anybody who has had a stroke”, she says. “But the film is about community. About the community that rallies around her.” It is crucial to cling to such fellow feeling, she says – just look at the US, where it’s been abandoned. There, money “is what you get judged by”.

The film has won particular praise for foregrounding a relationship not often spotlit in Hollywood: the adult son and elderly mother. “No matter your gender or sexuality,” says Flanagan, “everyone has a mother. And what is clever about this film is it shows the burden for a carer is huge, and that relationship doesn’t get a lot of attention. All those carers whose lives are – literally, from morning till night – thinking about another person all the time,” she continues. “Having to put their own desires and wishes and dreams aside and go to bed every night exhausted.”

Four Mothers also offers a rare representation of unglamorous older women on the big screen – a world away from the immaculate leads of, say, Book Club. Despite that film’s commercial success, and the continued popularity and box office pulling power of actors such as Meryl Streep, older women are still seen as unattractive to studios, Flanagan believes. A paradigm shift would be needed to change that.

“We have been led to believe that intelligence is the domain of mainly men. For women – pardon the expression – it is their fuckability which is taken into account.”

Flanagan was born in Dublin in 1941. Her father was an officer in the Irish army, a communist and veteran of the Spanish civil war. Neither of her parents spoke Gaelic, but they were sufficiently committed to Ireland to insist that all five of their children became fluent.

She cut her teeth at the Abbey theatre, specialising in James Joyce plays and quickly rising through the ranks. In 1968 she opened on Broadway with Brian Friel’s Lovers, after a national tour in which she was struck by the US’s student radicalism: “The campuses were in flames.”

Such activism, she laments, is now in short supply, particularly in an entertainment industry gripped by anxiety over Trump. “There is a lot of nervousness in LA,” she says. “But just wait until he takes away our [entertainment industry] unions, because they are full of people who, for the most part, disapproved of him and his policies.”

We meet a few days after the catastrophic meeting between Donald Trump, JD Vance and Volodomyr Zelenskyy at the White House. She is still reeling from watching the encounter. “It was shocking, shocking,” she says. “They have no manners. They are a bunch of hooligans, as my mother would say, headed up by the hooligan-in-chief. There is no humility, which in my opinion should be a prerequisite for the top office of the United States.” She allows herself a wry smile. “I am so cynical about America.”

She quotes Martin Niemöller’s poetic First They Came, about the conspiracy of silence over the Holocaust, and says she is “afraid that is very much the way it will be” unless those who do not support Trump revolt in meaningful ways.

Keir Starmer, she thinks, has so far acquitted himself well in comparison. “He’s become the star of the hour. Leadership takes someone not just with common sense, but with humanity, which is certainly not on display in the Oval Office.”

Flanagan seems an actor out of time in modern-day Hollywood: she speaks her mind and puts her money where her mouth is. She has been a donor to Sinn Féin and has been vocal in her support of the party for decades.

She encountered a considerable backlash for starring alongside Helen Mirren in the controversial 1996 drama Some Mother’s Son, playing the militant mother of a Provisional IRA hunger striker. “The press was vicious,” she recalled of the period in 2012. “They didn’t touch Helen because she was their darling. But they behaved towards me as if I was an IRA bomber. It was appalling.”

In 2002, she spoke at a memorial hosted by Sinn Féin for republicans killed during the Troubles, and seven years later joined Gerry Adams on a US lecture tour. Her support for Martin McGuinness’s 2011 bid for Ireland’s presidency brought more ire. But the following year she denied accusations of being sympathetic to either their cause or their methods.

“I got involved because of the peace process,” she told the Irish Independent. “That is why I did it. I wouldn’t have become involved otherwise.” When a reporter for the Sunday Times told her she was hosting a “reception for murderers” she replied, facetiously, “I hope so – I wouldn’t go to this much trouble for anyone else.”

Flanagan is still a formidable force on stage, too – she starred in John B Keane’s uncompromising masterpiece Sive at the Gaiety theatre in Dublin last year, and in Sam Mendes’s Broadway production of The Ferryman back in 2018. More stage work would be a great consolation for quitting America, she says, citing Mrs Tancred in Sean O’Casey’s Juno and the Paycock as her dream role.

“I am a theatre animal,” she says. “I could live in a theatre. My prayer is that I’ll drop dead in the wings at the end of the third act.” Another wry smile. “That way they won’t have to make excuses to the audience.”

• Four Mothers is in UK and Irish cinemas from 4 April and screens at the BFI Flare festival in London on 26 and 28 March