Remember as well those early imager tubes only had a few hundred hour operational lifetime, were rather insensitive ( thus the need for 50kW of light and a 200 ton AC unit in each studio), plus also had to be warmed up for around 4 hours before they would stop drifting, and could be aligned and set up using a massive colour chart and test pattern, daily. They also would have long term drift as well as the components aged, and many were also very orientation sensitive.
The rest of the world learnt from the US adoption of the National Television Standards Committee system, mostly in how to improve the very obvious flaws inherent in the system, and how, with only a few years better design experience from the original standard, designed to be compatible with the most common original set designs so as to not make undue interference, and made a few changes that improved stability and colour rendition.
Most obvious was PAL and SECAM mostly removed the "Hue" control, as the colour was a lot more stable both over time and with distortion in the transmission chain. The most impressive improvement prior to the all digital channel was that the designers of the standards managed to fit, in the original 8MHz allocated bandwidth, both colour pictures, analogue stereo audio, digital information ( Teletext) and as well high quality digital stereo audio ( NICAM stereo, which was capable of near CD audio quality, sadly let down by the poor speakers in most sets, being the smallest and cheapest they could fit in the set that would produce sound) which was the final step.