06/03/2013 08:29 GMT | Updated 05/05/2013 06:12 BST

'Brexit' Will Weaken US-UK Relationship

When many Americans worry about a crisis in the United Kingdom, they think of the deaths of Sybil and Matthew in Downton Abbey. While this fictional situation might be important to the show's followers, Americans should be more concerned about Britain's potential exit from the European Union. British Prime Minister David Cameron recently announced that his government wants to renegotiate the terms of British membership in the EU and hold an "in or out referendum" on EU membership by 2017. Although Cameron's proposal might appeal to the more conservative elements of British society, a British exit from the EU (often referred to as "Brexit") would significantly weaken its relationship with the United States, its most important ally and a global superpower.

The United States and United Kingdom have close historical and cultural ties. Given the US' status as a former British colony, American society has been heavily influenced by its former rulers. Its shared English language has enabled the two countries to develop deep and meaningful cultural exchanges. British and American Students flock to the other country's universities, successful Broadway and West End shows are able to cross over the Atlantic, British music stars hold the top slots in US Billboard charts and the National Football League holds at least one American football match in London every year.

While cultural engagement plays a key role in the US-UK relationship, this alliance is based primarily on political cooperation. Both sides require the other's assistance to achieve their objectives in the international community. The US needs Britain's approval to gain external support and legitimacy for its policies, while the UK relies on America's military power and international reach to achieve a greater voice in global affairs. This political relationship dates back to the World Wars when the US and UK fought together on behalf of democratic values.

In more recent years, the UK has been an important ally of the US in European Union negotiations, such as discussions dealing with trade and security in the 27 member state bloc. The UK represents its own interests in EU affairs, but the US has been able to take advantage of its key alliance with the UK to have Great Britain present American preferences in EU deliberations. For example, the US lobbied the UK to prevent a plan for the European Union to develop its own defense community separate from NATO. Although the EU established a Common Security and Defense Policy, the UK successfully petitioned on the US' behalf to ensure that CSDP would only be a fairly limited security initiative that did not present a threat to NATO and US security interests.

The UK would no longer hold as special a position in US foreign policy interests if it were to withdraw from the EU. The US would increasingly have to look to its other EU allies, rather than the UK, to advocate on its behalf in EU negotiations. The US-UK relationship, while incredibly vibrant, is not necessarily permanent. The UK's importance to US foreign policy would be diluted if it were to exit the EU or become a second class member. This is precisely why US Assistant Secretary of State for European Affairs Philip Gordon made a statement discouraging the British government from trying to leave the EU, a rare public rift between these two allies.

I sympathize with British concerns about the future of the European Union and its growing influence over its member states. However, the UK should attempt to reform the institution from within, rather than withdrawing from it, as a "Brexit" would reduce the UK's influence in European politics and put its special relationship with the US at risk. Given the importance of the transatlantic relationship to Great Britain, Cameron should be concerned about the future of this key alliance and avert his current plan.