Well the mainland of Russia and USA is 55miles, separated by the Bering strait.Russia is only 4 kilometres from America.
As Michael Caine would say... "not a lot of people know that"
However, in the middle there are 2 islands Little Diomede (U.S.) and Big Diomede (Russia) which are only 2.4miles apart.
And a weird fact, the international date line passes between them making 23 hours difference in time