Britain lurches ever closer to the European Union's exit door.
As a British millennial committed to our partnership with the United States, I'm worried. Americans should be, too.
By this time next year, America's "closest and most reliable ally" (as the Congressional Research Service says many U.S. policymakers consider Britain to be) may become the first ever country to vote to leave the EU in the institution's 60-year history.
While President Obama has voiced his concerns about Britain leaving the EU, both Sen. Marco RubioMarco RubioGlenn Beck: I was wrong about Ted Cruz Senate rivals gear up for debates Rubio: End of Obama's term could be 'most damaging yet' MORE (R-Fla.) and former Gov. Jeb Bush (R-Fla.) have signaled cautious support for Brexit. Democrats and Republicans alike should be anxious.
Prime Minister David Cameron's pledge in January 2013 to hold a referendum on Britain's EU membership was a calculated political move. Assuming he can negotiate a restriction on migrants' benefits in the U.K., Cameron himself is said to support continued E.U. membership. The prime minister has offered the British people the opportunity to determine the country's future relations with the continent.
At first, it seemed to work: Cameron's gamble helped the Conservative Party to win over Eurosceptic voters in an unexpected and decisive general election victory earlier this year.
But it's now clear that the gamble has backfired.
Just a year ago, 61 percent of the British public opposed leaving the EU. Yet there is growing popular frustration with perceived waste and inefficiency in Brussels, fomented by a well-funded and well-organized "Out" campaign. Today, voters are evenly split.
The Conservative Party is now divided by a civil war over Europe reminiscent of the Prime Minister Margaret Thatcher era, with "most Conservative parliamentarians," according to The Guardian, defying the prime minister in their support for the U.K. leaving Europe.
Brexit is now a very real possibility in 2016. This would affect America's national interests in a myriad of ways.
Trade relations with the United States would certainly be damaged. The U.S. will gain $95 billion per year from a free trade agreement with the EU set to be concluded within the next year. But the U.K. would be excluded from this Transatlantic Trade and Investment Partnership (TTIP) if it leaves. This would also reduce the benefits of TTIP for the U.S., given Britain's status as Europe's second largest economy.
British Eurosceptics have justified cutting Brussels loose on the grounds that we will be able to "stay within some sort of free trade agreement with America." However, the U.S. Trade Representative has categorically ruled out such a deal: We would be subject to the same trade restrictions as China, Brazil or India.
Brexit could have consequences for American jobs, too. British businesses and affiliates employ almost 1 million American workers, and over 90 percent of Britain's fastest-growing enterprises believe an "out" vote would be bad for business. We should heed this emphatic endorsement of continued EU membership from the private sector.
U.S. national security would also be compromised if Britain votes to leave Europe.
Growing up in southwest England, it's all too easy to forget just how recently our country was devastated by war. My grandparents' neighborhoods were damaged in air raids; their families evacuated; their friends wounded or killed. The physical and mental scars of war in Europe linger.
The European Union is one of the most successful experiments in post-conflict reconstruction in human history, and was awarded a Nobel Peace Prize in 2012. France and Germany fought three wars over 70 years. Conflict between Berlin and Paris is now unthinkable: their peoples united in friendship and respect, their economies interlinked. In large part, that's thanks to the E.U.
Today, we face altogether different, but nevertheless substantial, threats to our security, as demonstrated by a score of violent terrorist attacks across the continent in recent months. The proliferation of extremist networks — including, but not limited to, the Islamic State in Iraq and Syria (ISIS) — across Europe directly threatens American national security. European countries must work together to counter violent extremism, identify and disrupt safe havens for terrorist networks, and effectively police sovereign borders.
It will be harder, not easier, to marshal and finance integrated European counterterror operations if Britain withdraws from the EU. Homeland security on both sides of the Atlantic will be threatened, not reinforced.
A post-Brexit British society would be more inward-looking, isolated and insular than it is today. These values are antithetical to the moral foundations that underpin our special relationship with America: a proud commitment to liberal internationalism, democracy, human rights and free trade.
In the interests of our mutual prosperity and security, America must hope that the British people embrace a future at the heart of the European Union.
The challenges that the next president of the United States inherits may be all the greater if they do not.
O'Bryan is a U.K. Kennedy Scholar at Harvard University, representing Britain's living memorial to President John F. Kennedy. He is also a U.S. State Department Young British Leader and former policy adviser to the Liberal Democrats. Follow him on Twitter @TomOBryanHKS.