Cofiwch Dryweryn. These words – “Remember Tryweryn” – crudely scrawled on a wall near Aberystwyth in the 1960s, serve as a memorial for Capel Celyn, the Welsh-speaking village that was flooded to provide water for Liverpool, some 67 miles away, in 1965.

Liverpool city council officially apologised for its actions 40 years later, in 2005, but the mural commemorates a painful and pivotal period in Welsh history which had far-reaching consequences for Welsh politics, including the significant loss of Labour seats to the nationalist party, Plaid Cymru, in 1966. It could be argued that if Capel Celyn hadn’t been drowned, the Welsh assembly wouldn’t have been established just over 30 years later. That’s what “Cofiwch Dryweryn” stands for.

Over the last few days and weeks, the wall has been defaced, obscured and even partly demolished. Although there are no clues to why, or who is responsible, it’s clear that this isn’t mindless vandalism – this is a targeted anti-Welsh campaign to destroy a symbol of the country’s language, heritage and culture. But whatever the intentions of the perpetrators of this hate crime, they could scarcely have imagined the impact that it’s had on galvanising communities all over Wales. Now copycat “Cofiwch Dryweryn” graffiti is popping up all over the country – in Bridgend, Swansea, Llangollen, and Flintshire. There’s even demand for “Cofiwch Dryweryn” T-shirts.

It is significant that this is happening across Wales, in Welsh-speaking and non-Welsh-speaking communities – it is a recognition of a shared history and a declaration of a shared objective that I’ve never witnessed before.

My hometown, Bala, is three miles from the Capel Celyn reservoir. Llyn Celyn, as it’s known now, is where every local teenager is taken by their parents to learn to drive on the flat, barren road around the lake. Some 75% of Bala’s residents speak Welsh as a first language, and 95% of its children are educated exclusively in the Welsh medium. I’ve lived and worked across the border in England for 15 years so I understand that, for some, the concept is mind-melting that on the same island, just a short car journey away, there’s an entirely distinct culture, language and way of life. It may be even more surprising, when the majority of Welsh voters voted to leave the EU, that the movement for an independent Wales, Yes Cymru, is starting to pick up pace, with the campaign’s research suggesting that support for independence has grown from 10% to 19%.

‘Capel Celyn was flooded to provide water for Liverpool, some 67 miles away, in 1965.’ Photograph: Don Mcphee/The Guardian

Wales has been largely ignored in the chaos of Brexit, and a growing number of its four million inhabitants feel – as do many in Northern Ireland and Scotland – that their country would be better off within the EU, despite the initial vote to leave. This year, Charlotte Church fronted a series of sellout cultural events that discussed the future of post-Brexit Wales, and All Under One Banner has planned a march for Welsh independence in Cardiff on 11 May.

Now, I don’t think I’m a nationalist. I’m not sure (whisper it) that I’m even particularly patriotic – isn’t it a bit weird to be proud of something that you have no control over? Isn’t being proud of where you were born almost as absurd as being proud of your star sign?

But while I may not wake up every day and thank the Lord that I’m Welsh – as Cerys Matthews professed to – I am genuinely thankful that by an accident of birth I’m part of a nation with a rich cultural history, its own wondrous language (that I’m rediscovering, to my delight, through contemporary authors such as Manon Steffan Ros), and an exciting future.

The desecration of the Tryweryn memorial has sparked a resurgence of a new nationalist spirit, new hope for the people of Wales, new political engagement and a desire to explore what our country could become. I want to know what resources Wales has that we could choose to keep for ourselves or share with the world if we weren’t under the cosh of Westminster. What would an independent Wales mean for those of us who live and work beyond the boundaries of the land of our fathers? We don’t know the answers to all of the question but we can find out. In the wake of anti-Welsh witlessness, Wales is waking up.

• Michelle Thomas writes about mental health, body image and dating. Her first book, My Sh*t Therapist, is out in June.