Samsung's transistors are only slightly behind TSMC, SS8nm probably trades blows with intel 10nm and solidly beats 14+++. And their DRAM and NAND flash is the probably the best, so it is at least comparable.

But beyond SK I cannot think of any other countries with competitive fabs.

Also only a tangent but I really believe that deal where TSMC is going to put a N7 fab in the USA is either going to get restructured into something way smaller or never ever going to happen.

Sony dominates imaging sensors.

Sorry, yes south korea has an amazing industry. Japan too even if it's not the leader it used to be. but even then, last gen chip design is overwhelmingly coming from the US. Apple, AMD, Qualcomm and Intel have the most performant designs by far, so the moat is still definitely present. Taiwan and SK are arguably better in manufacturing the chips right now though I agree.

I remember that Fujitsu fabricated the SPARC processor, but what other semiconductors is Japan known for?

Pezy SC was kicking around top500 for a while, Sony domminates imaging sensors, likewise for sending niche medical and electrical stuff.

Kioxia (formerly Toshiba Memory) is large semiconductor for NAND chips, its fabs are in Japan.