If the private key of a Time Stamping Authority (TSA) were to be compromised then any timestamps issued by that TSA would lose verifiability. This would mainly mean that the use of such a timestamp wouldn't be valid in court for proving that a contract was signed on such-and-such date.
Does it is a single point of failure to all the SSL/TLS certificates?
TLS certificates don't use Time Stamping Authority values. Public CAs now send certificates to Certificate Transparency logs; but Signed Certificate Timestamp values don't have anything to do with Time Stamping Authorities.
Even for things which were cryptographically timestamped, the person requesting the timestamp can usually request timestamp values from multiple parties. As long as at least one of them had never had a key compromise (or evidence of clock tamper) then their timestamp value would still be considered authoritative... keeping the document considered appropriately timestamped.