There are multiple critical points of failure
Some of the known critical points
TSMC - obvious - over 50% of high performance IC production
AMSL - producer of all the EUV machines and most of the DUV machines
ZEISS - makes the optical components (lenses and mirrors) for AMSL
AGC Inc and Hoya Corp - these make the blank photomasks
multiple companies producing critical ultra pure chemicals (with impurities in the parts per trillion range) and photoresists