The thing though is - and maybe the GP was trolling and I'm falling for the bait - as far as the rest of the world that is not North America (and maybe Japan too) was concerned, the Spectrum *was* a world-wide phenomenon. He could have used the argument that the C64 was technically superior, and then there would be few people to argue that. But market-wise, as you correctly pointed out, the Spectrum beat the shit out of the C64, and not only on the UK, but most of the world.
Case in point: I'm from Brazil, we didn't have legit Spectrums here back then, but we had locally-made clones, which amounted to the same thing and ended up getting exported to all of South America, and you know what? The only way anyone on Latin America knew the C64 actually existed was that it was often mentioned on computer magazines, and that was it - I never knew anyone who even heard about of the C64 around here, let alone owned one. We heard a lot about the TRS-80, Apple II (or rather its clones that were produced locally), MSX and so on, and it wasn't uncommon to find users of such systems, but the C64? Nada. I understand the C64 actually managed to chew a bit more of the market on some parts of europe, but the Spectrum was still far more popular. IIRC, on Russia the situation was similar to South America, in that they had Spectrum clones, and the C64 was a computer only the US cared about.