In 1930, the British Daily Mirror issued a weather report, "Fog in the Channel, Continent is isolated."  Britain is an island nation, with no borders except the sea.  It has not been invaded by foreign troops on the ground since 1066, nor has it had or claimed possessions on the European content since 1558, when Calais was lost, though the 2.6 square miles of Gibraltar are still British territory.

This island nation also until the 20th century ruled half the world, the largest empire in history, on which the "sun never sets."  Britain was both the workshop of the world and its global power.  Karl Marx in his Communist Manifesto of 1848 saluted the country, which, in addition to being the leading capitalist power,  "has accomplished wonders far surpassing Egyptian pyramids, Roman aqueducts, and Gothic cathedrals."

Memories of Britain's greatness are still voiced every year at the opening of the Proms Musical Festival in London.  The orchestra plays the 18th-century song Rule Britannia, a song about power, with its regal sentiment that, "Britons never, never, never shall be slaves."

No one is suggesting that Britons are slaves because of the British connection with the European Union, but the political struggle has now been intensified between those Britons wanting to remain in the EU and those who want exit (Brexit).  The most recent poll shows that 51 percent of the British favor remaining while 39 percent want Brexit, and 10 percent don't know.

The physical isolation of Britain and memories and echoes of its past greatness are at the heart of the ongoing relationship, with its complicated economic and political factors now even more difficult because of the migration problem among Britain and the 27 other nations of the European Union.  Since January 1973, when Britain joined what was then called the European Economic Community, which led in 1993 to the EU, and ended its preferential ties with its former colonies, it has been a member of the enormous common single market of 500 million in Europe with free movement of goods and people.

However, there has been constant criticism of British membership of the EU.  A referendum in 1975 voted in favor of remaining.

In January 2013, Prime Minister David Cameron, facing a political challenge by UKIP at the forthcoming election, promised to put the question of Britain's membership to the people by another referendum.  He has been faced with a host of problems: division within his political Conservative party and within his own Cabinet, including Michael Gove, minister for justice and close personal friend, and his political rival Boris Johnson, mayor of London, and strong differences with some of the EU countries and European officials, like Jean-Claude Juncker, EU president, and Donald Tusk, president of the European Council.

Cameron said he would seek from EU members a "new settlement" for Britain and discuss concessions from Brussels.  After prolonged discussion and all-night negotiation on February 19, 2016, a deal was reached between Britain and the other 27 members of the EU.  It was a compromise, dealing with some difficult and detailed issues but omitting the general one of the exact future of the EU.  The detailed issues do not concern the United States in any real way, but the general issue of the nature and destiny of the EU, and its relationship with the U.S., does.

The deal will become the basis of a referendum to be held on June 23, 2016: should Britain remain a member of the EU or leave it?

There are two crucial issues.  Has membership of the EU, open and competitive, helped or hindered the British?  And there is the question of the sovereignty of Britain and the likelihood or unlikelihood of an "ever closer union" of Europe.

On the first issue, the set of economic issues, any definitive answer is arguable.  Britain lagged behind France, Germany, and Italy, the founding members of the EEC, but for the last 40 years its GDP per capita has grown faster.  Does Britain give more than it gets?  Figures are not easy to assess, but critics of EU membership estimate that being a member costs Britain more than £20 billion a year.  In return, it gets £4.5 billion in aid and agricultural subsidies, and the private sector gets about  £1.5 billion.

Trade liberalization improves competition and has increased growth.  The U.K. is the world's fifth largest economy, and the EU is its second.  The EU imports 45 percent of British exports and accounts for more than half of British imports.  At the same time, Britain is the least dependent country in the EU for export revenue to EU countries.

There is disagreement on the impact of the EU on British jobs.  Some argue, and others disagree, that leaving the EU will cost 3 million jobs, those associated with exports and services to other EU countries.

Immigration has not added much to British prosperity, though it has benefited the migrant workers.  Curiously, in the negotiations in February, much of the discussion and the conclusion concerned work benefits, migrant welfare benefits, maintaining the pound and not joining the Eurozone, and tax credits for migrants and benefits for children of EU workers.

On balance, Britain has benefited from openness to world markets and economic dynamism.  Leaving the EU would jeopardize the gains Britain has made.  At the same time, Brussels favors a large EU budget and free movement within the EU, while Cameron wants to cut spending and to discourage Polish workers from entering the U.K.

The crucial hanging issues are whether the EU has reduced British sovereignty and whether Brexit will restore it.  And has it helped British security?  The issue has overtones for American politics.  The EU – its political apparatus, its large bureaucracy, its judicial system – attempts to centralize power in Brussels, which has led to economic mismanagement and problems with dealing with immigration from the Middle East.  Britain has challenged a number of those Brussels policies.

Nevertheless, Cameron's argument is that leaving the EU would be a dangerous thing in an uncertain world and that the U.K. will have more influence on security issues because of EU cooperation on issues such as crime, cyber-attacks, and terrorism.  The problem with this is that the EU has not been capable of agreeing on an effective foreign policy.

For the British nation, there are pressing concerns that may arise on the result of the referendum.  One is that the Conservative government may fall.  Another is that if Brexit wins, Scotland may break away from Britain and vote for independence because it is pro-EU.  Another is that other EU countries may want concessions from any general EU agreement.  Immigration remains a problem, increasingly difficult, now that countries are raising barriers against migrants from the south.

Above all, there is the general problem.  Cameron succeeded in getting a commitment that Britain will not be part of the EU objective of an "ever closer union," and that some limits will be imposed on free movement.  The conclusion for American politicians to consider is that it is the better part of wisdom for Britain to remain now that the EU will not compel all member states to aim for a common destination.  Britain is not committed to further political integration into the European Union.  It will keep its strong relationship with the United States.