What is the greatest ally of the United States?

[politicus]

I'd argue that the closest "natural" ally of the United States is Great Britain by virtue of our shared history, language and culture, and the fact that we would not exist as a country were it not for Britain.

They did their best to stop you from becoming a country.

[politicus]

Write-in: Turkey

[politicus]

I think Canada is really the instantaneous, obvious answer, since other countries are further away and their interests may diverge more. Israel (an important, close ally, but not on Canada's level) just gets a lot of attention because of how frequently it conflicts with its neighbors. I'm a little confused at why everyone is overwhelmingly answering the UK -- doesn't practically every argument in its favor apply even more strongly to Canada?

Likely because the UK has been your most important ally in recent wars. It is also a much stronger power than Canada, so it depends how you define "greatest".

[politicus]

For once, I agree with Vosem entirely.

Doesn't the term greatest imply something more than closest?

[politicus]

Britain is the majority view - with Russia as greatest threat.

http://www.pewglobal.org/2014/07/14/global-opposition-to-u-s-surveillance-and-drones-but-limited-harm-to-americas-image/pg_14-07-10_alliesthreats_640px/

[politicus]

It seems most countries perceive greatest ally as most important/strongest ally:

[politicus]

Canada with the UK a close second.  Japan and Australia tied at a distant third.  Everybody else lower and with a lot more change in the order, sometimes changing rapidly.

Criteria?