While countless eyes in America are focused on our presidential primary dramas, another rapidly approaching election has the potential to change the world in unforeseeable ways. Yet it barely garners attention in this country.

I refer to the June 23 referendum in the United Kingdom, which will determine whether or not the UK remains a member of the European Union.

“So what?” you ask. “Why should I care about such an arcane matter?”

The answer is twofold. Not only would a British vote to leave the EU be unprecedented, but a “leave” vote could set in motion a host of unpredictable and potentially disruptive events that would be felt in America and elsewhere.

First some background. The idea of European unity was forged in the aftermath of World War II, the second global conflagration with origins in Europe.

In 1952, six former adversaries — Belgium, France, Germany, Italy, Luxembourg and the Netherlands — formed the European Coal and Steel Community, placing their heavy industries under common management. The goal? No member country could rapidly mobilize and make weapons to turn against the others, as in the past.

Next came the European Economic Community, ultimately comprising 12 countries. By binding themselves together through closer trade and economic ties, the thinking went, countries would be far less likely to go to war against each other.

The more comprehensive European Union was created in 1992-93. It aimed for a common foreign and security policy; closer cooperation on justice and home affairs; and economic and monetary union, including a single currency. It included “four freedoms” of movement — of goods, services, people and money.

The EU now has 28 members, of which 19 are Eurozone members, sharing the Euro currency.

European unity has, in many ways, succeeded beyond the imagination of its founders.

EU member countries have been at peace for longer than at any time in their history, and they rank among the world’s wealthiest. Their record of peace and prosperity has served as a model for many other countries, while Europe’s advanced economies have helped fuel our own and other countries’ growth and prosperity through extensive trade and investment ties.

Equally importantly, Europe shares many American values — including support for democracy, human rights, and the rule of law. These shared values make European nations important partners in shaping global rules and norms for all countries to live by.

But many of those values, as well as the glue that has held Europe together, are being tested as never before. Europe’s economies still struggle to recover from the 2008-2009 global financial crisis and recession; the Eurozone faces ongoing threats to its existence; and the unprecedented flow of refugees from war-torn and other nations places serious strains on Europe’s emergency resources and its people’s tolerance.

Recent elections have strengthened far-right and far-left parties that previously struggled for respectability and votes. And critics of the EU say its bureaucracy has become too heavy-handed and unaccountable to people in member countries, saddling members with rules and regulations that stifle national prerogatives, growth and identity.

The UK referendum takes place in the midst of this turmoil. Voters will be asked a simple question: "Should the United Kingdom remain a member of the European Union or leave the European Union?"

British Prime Minister David Cameron negotiated a “special deal” giving the UK exemptions from some EU rules, including those involving payments to immigrants and their families. While public opinion polls show a narrow margin of support for the “remain” camp, much can change between now and the time of the vote.

Economists on both sides have issued prognoses of the impact of a vote to leave: either it will be dire, bringing recession and financial instability; or it will allow the UK economy to soar, free of burdensome regulations.

The economic impact is hard to foresee. What is easier to foresee is the political and psychological impact of a vote to leave.

The UK has been a key player in all aspects of EU life and often has used its position to push for closer alignment of EU policies with American initiatives. Losing that voice — potentially along with the EU’s largest military — could weaken the EU as an American partner.

Moreover, leaving would likely strengthen other separatist or nationalist movements in Europe (Scotland/UK; Catalonia/Spain; National Front/France, etc.), putting more pressure on European cohesion.

Russian President Vladimir Putin, who is working hard to provoke splits in European unity, surely would be delighted by a UK vote to leave the EU.

Joanna Shelton was deputy secretary general of the Organization for Economic Cooperation and Development in Paris; held senior positions in the executive branch and Congress in Washington, D.C.; and teaches at the University of Montana. You can reach her through her website, joannashelton.com.