No other international alliance seems to come under the intense scrutiny reserved for the one between Britain and the United States. There is a seemingly endless British preoccupation with the health of the special relationship. Its temperature is continually taken to see if it's in good shape, its pulse checked to see if it will survive.

I have never understood this anxiety. The U.S.-U.K. relationship is simple: It's strong because it delivers for both of us. The alliance is not sustained by our historical ties or blind loyalty. This is a partnership of choice that serves our national interests.

There are three sets of critics who seem to fret incessantly about the relationship: those who question the whole concept, those who say it is no longer "special," and those fixated on form rather than substance. Each of them is misguided.

The first group seems to view America as some sort of "evil empire," a country that is too powerful, that does nothing but sow discord in the world. They say Britain should have much less to do with America. I say they are just plain wrong.

The U.S. is a formidable force for good. Together we fought fascism, stood up to communism, and championed democracy. Today we are combating international terrorism, pressing for peace in the Middle East, working for an Iran without the bomb, and tackling climate change and global poverty.

Then there are those who claim the U.S.-U.K. relationship was special once but not any longer. 

They argue that the U.S. doesn't care about Britain because we don't bring enough to the table. 

This attitude overlooks our unique relations across the world—throughout the Gulf States and with India and Pakistan, not to mention the strong ties with China and our links through the Commonwealth with Africa and Australia

There's also the professionalism and bravery of our servicemen and women who have spent much of their careers serving alongside Americans in the world's combat zones. And the skill and close relationship of our intelligence agencies.

Finally, there are those who over-analyze the atmospherics around the relationship. They forensically compute the length of meetings; whether it's a brush-by or a full bilateral; the number of mentions in a president's speech; dissecting the location and grandeur of the final press conference—fretting even over whether you're standing up or sitting down together. This sort of Kremlinology might have had its place in interpreting our relations with Moscow during the Cold War. It is absurd to apply it to our oldest and staunchest ally.

I know how annoying this is for Americans, and it certainly frustrates me. I am hard-headed and realistic about U.S.-U.K. relations. I understand that we are the junior partner—just as we were in the 1940s and, indeed, in the 1980s. But we are a strong, self-confident country clear in our views and values, and we should behave that way.

Mr. Cameron is the British prime minister. To continue reading his column in The Wall Street Journal, click here.

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