As stated on that page, motor gasoline was 45% of US petroleum consumption, so 23% of that 68% wouldn't be touched by electric cars. There's also a relatively small amount that ends up in small engines[1], but I'm willing to write that off as a rounding error.

[1] Side note: I'm impressed by the explosion of high-quality electric replacements for small gasoline engines over the past few years. All my power yard tools are electric; the only gasoline engines we own our the car and the generator.