No it's not, the two have nothing to do with each other. Sega was already ahead in the US there wasn't a competitor they Needed the Sega CD to compete with.
dont know about country sales numbers but gaming was not really mainstream back then hence the overall low numbers.
that changed with playstation
Even with Playstation gaming wasn't mainstream it just attracted new demographics that replaced the ones lost before and that generation ended up selling a similar amount of consoles.
People were just not as hyped with the Genesis and SNES in the long term. The drop in the gaming industries profits showed this when in 1992-1996 gaming went from $7 billion to 2.3 or 2.5. 3D and new genres that were appealing to broad groups of people was needed.
You are under the wrong impression that PCE had sold markedly more than MD in Japan, which isn't true.
Comparatively the one aspect PCE was dominating over MD in Japan was in the CD players install-base, the ratio was close to 5:1.
In Japan the base PCE has sold 3.77M, the Duo models around 1.00M and lastly the Rom^2 add-on around 1.00M (PCE "CD players" userbase was close to 2M).
Only considering the standalone consoles and excluding the portable units, PCE TV consoles total sales in Japan were around 4.8M units.
Meanwhile Mega Drive has sold 3.58M, Mega CD 0.40M and Super 32X around 0.05M.
So PCE outsold the Mega Drive in Japan but not by much.
Japanese Shipment data from NEC HE:
Few issues here, there's little evidence the PCFX sold 100,000 units so having nearly 200,000 on the shelves doesn't make sense to me, after the first shipment the low sales would be obvious so why would they ship another 120,000? Of course, ther's shipments that suggest that the PCFX shipped 400,000 and 500,000 to the numbers all seem to be unreliable.
Another thing, All the CD's were called CD ROM^2, unless they were Super CDs or Arcade CD, most likely you're thinking of the Super CD add-on.
Going to Sega, they used shipment numbers to make it look like the sales were close but they weren't, the PC Engine software sales trounced the Mega Drive and very few games did well even any standard. The PCE CD made things worse for Sega because it took off in Japan which increased software sales even further, while Sega was cutting the Mega Drives price to be more affordable but people were barely buying games for it the attach rate was bad. Sega CD also failed to gain traction like the PCE CD, Japanese consumers were not interested in the software.
You can tell at least 5 million PCE/CD/Duos were sold before NEC destroyed their momentum because of not only the CD revision console sales, but because the shipment numbers grew past 5 million.
In FY92-93 NEC shipped 670.000, the shipments were already over 5.2 million then, and there were 3 more fisical years of shipments after that for the PC Engine ending with a final total of 5.8 million.
In Japan, during that same FY Sega did not even ship 3 million Mega Drives yet, that happened the next FY, and NEC had software sales far ahead of what Sega had on both card and CD, to act like it was close or not my much is wrong.
Now it wasn't a major victory for NEC, at least before the DUO, and both Sega and NEC had poor software sales compared to what the SNES brought in which was the fault of NEC and HUDON marketing weird games without vetting them and not really centering their marketing around some of their top IP, which oddly enough DID happen in the US for some reason. But you are right in that it wasn't a landslide that people think it wasn't, but it wasn't close either.
Genesis got smoked... even with a skyscraper worth of add-on hardware, add-on chips, and a headstart, Genesis still lost the battle by a large margin.
SNES had many chips, but as said in the NEC/SEGA thread Sonic was the major instrument to Sega's success in America and parts of Europe, just America alone you could take 13 million consoles from Sega if it wasn't for Sonic, maybe more, as it's success made it more feasible for third parties like Midway to put Mortal Kombat on it.
When viewed from that angle, it makes sense that the consoles prospect declines with Sonics sales. If US sales were falling so fast in 1994, that by 1996 Sega had to take a $60 million write-off on unsold US inventory and SNES was still selling well that entire time then it's understandable how the SNES had the worldwide lead that it did. It only failed to win in Europe out of the major territories but still picked up sales there late in the gen.
It was disastrous for both companies. Ruined Sega and almost ruined Nintendo.
I don't see how CD almost ruined Nintendo, for one if anyone could have achieved moderate success with the CD Add-on it was Nintendo, in Japan NEC pulled it off, Nintendo was bigger than NEC their with better software support from 3P and FP, they were also a known brand in Europe and the US despite not doing to hot in Europe for consoles, but dominated handhelds. NEC did not have that.