That's the cool thing about analog video, it doesn't really have the concept of horizontal resolution. Especially when it's monochrome. It's made up of lines that continuously change brightness as they're drawn.
Color composite video, as far as I understand, does have a limit to the horizontal resolution because in all three standards the color information is encoded as a high-frequency signal added to the main (luminance) one, so that frequency is your upper limit on how quickly the luminance can change.
S-video, VGA, and component should, in theory, allow infinite horizontal resolution and color.