While the interconnects are certainly a very important part of a supercomptuer, they aren't the hardest part. Building a high performance CPU takes a shit ton of research and infrastructure. The barrier for entry is exceedingly high and takes a long time to spin up. You can see that with China's Longsoon processor which for all the hyped ended up being a license of a MIPS core, built on an old process technology. Building a ton end CPU is just tough stuff.
Of course then there's the other fact that there are plenty of interconnect makers that are not Chinese. The big names in high speed interconnects are Cray (US), IBM (US), and Infiniband (which is made by many companies like Intel and Mellanox). It's not like China has the high speed interconnect market cornered.
Finally there's the silliness of focusing on #1. Yes, they have the #1 computer at the linpack benchmark (which is not good at representing performance in all things). However the US has the #2, 3, 5, 8, and 10. In other words, half of the top 10. The idea that only the top spot matters is very, very silly.