Well, UTC didn’t exist in 1800, it would have been GMT, and that might not have been too popular so soon after the war of independence. Even if you convinced all of the USA to use one time zone for the railways, it would be different elsewhere and you’d still get time zones.
Maybe you’d get further with the project with the airlines in the first half of the twentieth century, but I’m not sure that that level of internationalism would have gone down well in a rather war torn world.