I thought it was the reverse. US shows of the time were so often dark. I'd heard there was a technical reason behind this: in NTSC, if the colours are too brigh

I thought it was the reverse. US shows of the time were so often dark. I'd heard there was a technical reason behind this: in NTSC, if the colours are too bright the video signal can leak into the audio channel causing annoying noises and PAL didn't have this issue. I haven't attempted to verify this however. I'm also unable to think of examples beyond X-Files, but that could well be for aesthetic reasons. I guess I didn't watch a lot of US TV back then.