The U.S. should maintain good relations with Britain, but I’m not sure that it’s true that Britain is “our most historically reliable and most legally and politically aligned ally,” as Matthew Feeney writes. If we measure reliability in terms of contributing to common war efforts, the Australians have actually been more reliable than Britain. The U.S. and Australia arguably have more in common as large Anglophone settler nations. We also probably have more in common with Canada in terms of political and legal culture than we do with Britain.
Shared history and culture are important, but shared history and culture didn’t require the U.S. to have any alliance with Britain prior to 1917, and the conditions that made military alliances with Britain useful and necessary have largely disappeared. It is desirable that the U.S. have good relations with Britain, but it isn’t at all clear that the U.S. needs or that the U.K. wants the sort of “special relationship” that has been mythologized and built up since WWII. On the whole, it would be healthier for both countries to have a cooperative political and economic relationship rather than an overly-militarized “special” one, which is what that relationship has been in practice for the last twenty years.
Something else to consider is that the U.K. as it currently exists may not be around much longer. If the U.K. is in the process of slow-motion disintegration, as Norman Davies suggests in Vanished Kingdoms, the U.S. will have to adapt to the emergence of new states, some of which may have little interest in forging close alliances with America. Davies imagines how the disintegration might start to occur:
When Scotland departs, a crestfallen England–frustrated, diminished and shorn of its great-power pretensions–will be left in the company of two far smaller dependencies. Resultant discomforts will grow sharply. Autonomous Wales will compete with autonomous Northern Ireland to make the next move. Timescales are hard to estimate, but in ten or twenty years’ time, political evolution may have progressed further in Ulster than in Wales. Throughout the twentieth century Ulster Unionists could afford to be intransigent, because they possessed a local, democratic majority; in the twenty-first century they will be squeezed by the growing demographic advantage of the Catholic and nationalist community.
It’s possible that the U.S. might continue to have closer ties with an independent England in the future, but I don’t see how or why the “special relationship” would survive the dissolution of the U.K., which could be starting in just the next few years.