The divides and borders between those peoples have become more defined and entrenched through Brexit, the Covid-19 pandemic and the rise of identity politics.
The Republic of Ireland is now the only nation still part of the European Union bloc.
In the United Kingdom, the weekend elections offered a snapshot of where the country is at through contests covering devolution, local authorities, a byelection and mayoral races in Scotland, Wales and England.
Incumbent, high-profile Labour mayors in London and Greater Manchester were returned, but England these days is swathed in Conservative blue.
As in the December 2019 general elections, the Conservatives are still making ground in Labour's old northern England heartland. The Tories gained the Labour stronghold of Hartlepool for the first time, with a 16 per cent swing in a Westminster byelection and picked up Durham County Council for the first time in a century.
Labour was battered in council elections, mostly by the Conservatives, although the Greens made impressive advances in councillor numbers.
Wales is still strongly Labour red, with First Minister Mark Drakeford's administration winning half of the seats. Drakeford said that "sovereignty is now dispersed across four parliaments in which we choose to pool it for common purposes. That's the sort of UK that I think will have the very best chance of surviving."
Labour in Wales has successfully branded itself a Welsh party as distinct from the national party, whose leader Keir Starmer is struggling against Boris Johnson, despite the Prime Minister's various scandals.
Starmer radiates calm, lawyerly competence but Labour needs to establish a connection and gain the trust of the person in the street. Being the figurehead requires different skills than a quality Cabinet minister.
The Scottish National Party once again dominated the devolved Parliament with 64 seats, just one short of outright rule. With the fellow pro-independence Greens getting eight, First Minister Nicola Sturgeon wasted no time in pledging a new referendum.
"Given the outcome of this election, there is simply no democratic justification whatsoever for Boris Johnson or anyone else seeking to block the right of the people of Scotland to choose our future."
The Westminister government would have to go to court to stop legislation for an independence referendum. Although the election confirmed the SNP's standing in Scotland, the timing of any referendum would be key.
There has been a drop in support for independence this year during the vaccination rollout, after the heights of nearly 60 per cent backing in public polling last year, reflecting months of pandemic disaster.
Covid-19 has pushed Brexit issues into the background but they can be expected to return as the coronavirus threat slowly eases. In the 2016 Brexit referendum, Scotland and Northern Ireland voted to remain in the EU, whereas England and Wales sought to leave. There is a Celtic curve of pro-European sentiment from Scotland down through the island of Ireland.
The Brexit slogan, fuelled by an English-centric nationalism, was ''take back control" - supposedly Britain running its own show from London rather than taking orders from Brussels.
But the pandemic has allowed people in Scotland and Wales, through devolution, to witness those administrations handling a crisis alongside the government in London, sometimes with different approaches, rules and timetables.
The UK looks to be set down a path of more taking back control, only this time from within.
