By JON WILLIAMS
ABC News
17th September 2014

Of all the many crises this summer — from ISIS, to Ukraine, Ebola to Libya — who’d have thought jolly old England would be on that list?

Technically, it’s the United Kingdom of Great Britain and Northern Ireland. But for how much longer? On Thursday, after 307 years, Scotland may vote for independence and with it, potentially change the world order that has lasted since the end of the Second World War. Decisions taken across the highlands and lowlands of Scotland will echo far beyond the shores of a disunited kingdom.

Fifty years ago, U.S. Secretary of State Dean Acheson declared that Britain had “lost an empire but not yet found a role.” He may have been premature. During two decades of war — in Iraq (twice), Afghanistan and elsewhere, Britain chose the role as America’s “ally-in-chief.” British and US troops fought and died together, from Basra to Helmand and beyond. Half a century after he dismissed “Great” Britain, on September 18, the Britain Acheson spoke of, may cease to exist.

A Kingdom of England, Wales and Northern Ireland would continue. But Britain would be partitioned – not for the first time. In 122 AD, the Roman Emperor Hadrian built a wall, stretching 75 miles to keep “barbarians” of Scotland out of England. Two millennia on, a vote for independence would consign Great Britain to the same history books as Hadrian.

The implications would be profound -– not just for the rump of the United Kingdom, but for the United States and the Western Alliance.

While Scotland makes up just 8 percent of the UK population –- its GDP of $235 million puts it just behind Connecticut ($240 million) -– it is also home to the 58 Trident nuclear missiles leased by Britain from the United States and the four nuclear submarines that carry them.

Scotland’s First Minister Alex Salmond –- the man who has led the march to independence –- has promised to remove the missiles and the submarines from their current base on the west coast of Scotland during the first term of parliament following independence. The consequences for Britain and NATO would be grave.

No other port in the U.K. is equipped to house the missiles, raising the potential prospect of Britain’s “independent” nuclear deterrent being based in France, or at the US naval base at King’s Bay in Georgia, home to America’s own Trident submarines.

And then there’s the flag. The Union Jack is made up of the flags of the UK’s constituent parts -– the red St George’s Cross for England, the red diagonal Irish cross of St Patrick, and Scotland’s blue white and blue Saltire. Officially, it’s even called the Union Flag -– so without a Union, what to do? It’s not just the U.K. that will need a rethink. Four other countries also have the Union Jack in their flag (Australia, New Zealand, Fiji and Tuvalu) as well as Britain’s overseas territories like Bermuda and the Cayman Islands. Even the state of Hawaii has the Union Jack in its design, as do the Canadian provinces of British Columbia, Manitoba and Ontario.

Next year the United Nations marks its 70th birthday. Across seven decades — for all of Acheson’s doubts -– the U.K. has been one of just five “great powers” to be permanent members of the U.N. Security Council, alongside the United States, Russia, China and France. But there are many who covet Britain’s UN chair. India and Brazil have been pushing for Security Council reform.

This week, even the former British Prime Minister, Sir John Major, warned that should Scotland vote for independence, the U.K.’s place as a member of the permanent five of the United Nations “would no longer be viable.” Others warn that it could lose its place in the G7 group of Nations. The IMF ranks the UK as the world’s sixth biggest economy. Without Scotland, the U.K. would be overtaken by Brazil.

Many of Britain’s nearest neighbors are also watching closely. The European Union says an independent Scotland would leave the E.U. and need to reapply for membership. Each of the E.U.’s 28 member nations has a veto on new members. Many have their own separatist movements. Spain would be unlikely to encourage Scottish independence for fear that Catalonia might be next.

While warning of the risks to the U.K.’s place in the U.N., former Prime Minister Major also warns independence would enhance the risk of Britain’s exit from the E.U. As if one in/out referendum isn’t enough, David Cameron has promised another — in 2017 -– on whether the U.K. should leave the European Union. But that would follow Scotland’s exit. And with more voters in Scotland pro-EU than in the rest of the UK, those fighting to keep Britain in Europe fear it could tip the balance towards the rump of the UK leaving the EU – the United States’ largest trading partner.

Five million Americans can claim Scottish ancestry, almost as many people as live in Scotland today. This time next year -– on September 11, 2015 — Queen Elizabeth will become Britain’s longest reigning monarch, passing Victoria’s record of 63 years and 216 days, an anniversary she will spend at Balmoral, the Scottish Castle where she is said to feel most at home. Through her mother, the Queen is a direct descendant of the legendary Scottish warrior Robert the Bruce. It would be a bitter irony if it was Britain’s most Scottish monarch ever who presided over the break-up of her United Kingdom.