US is part of the NANP which means they have their own system for beyond +1, which is shared with Canada and half the Caribbean, and so they were given the whole of +1 rather than +10, +11, +12 etc. all resolving to the same thing, or +10 being for about 10 different countries while +11 was for one
Then the Soviet Union wanted a single digit too, which is why Russia and Kazakhstan share +7
It’s interesting to me that the US, Canada, Russia, and Kazakhstan get single digit codes, and the rest of the world get double or triple digits.
US is part of the NANP which means they have their own system for beyond +1, which is shared with Canada and half the Caribbean, and so they were given the whole of +1 rather than +10, +11, +12 etc. all resolving to the same thing, or +10 being for about 10 different countries while +11 was for one
Then the Soviet Union wanted a single digit too, which is why Russia and Kazakhstan share +7