"You are what you eat" and this extends to what you drink - more than mere calories and nutrients. Unlike most foods, what you drink may also well contain...
You say that in the USA “proof” is equal to twice the ABV. I take it then that “proof” as was usually used in the U.K. (but now ABV is used) was different because I’m sure that 70° proof was equal to 40% ABV.
Anonymous