Let's not forget that when the ICAO proposed four-letter codes in 1947, the USA objected and said three-letter codes were sufficient...
Hmmm.. Interesting. I wonder what made them think that??? I will have to apply my historian skills to research this as I find it interesting.
The USA also decided to omit the "u" in colour, favour, and lord knows what else... in order to save ink.
With that philosophy in mind, using three letters because it satisfies your needs 98% of the time is quite logical.
Plus the USA doesn't have too many problems with foreign countries on their doorstep. Basically it's just Canada and Mexico.
And in 1947 aircraft were not routinely flying into US airspace from anywhere else, so who needs all these international identifiers?
The fact that the rest of the world has different issues (apart from maybe Australia & NZ) is not the USA's problem.
Now, when y'all finished throwing rocks at me, here's something that might be more relevant;
These airport codes are not really an invention of ICAO at all; the convention they follow predates that organisation, and are more related to radio callsigns thrashed out in the great Radiotelegraphic Conference of 1927.
A good place to start might be the ITU - but fair warning, it's part of the United Nations
Worse than that, they conduct proceedings in French. https://en.wikipedia.org/wiki/Internati ... tion_Union