Tony already knew Pussy was a rat, he was just in denial of it all throughout season 2. Finding the actual wire in Pussy's bedroom was just the moment where Tony has to say to himself, "what are you waiting for, an indictment with 20 life sentences?". When they served the warrant at Tony's house after Livia gets detained at the airport, Tony had to be thinking he waited one day too long to deal with the Puss problem. He looked relieved when they told him it was just the airline tickets.

"...the successful annihilation of organized crime's subculture in America would rock the 'legitimate' world's foundation, which would ultimately force fundamental social changes and redistributions of wealth and power in this country. Meyer Lansky's dream was to bond the two worlds together so that one could not survive without the other." - Dan E. Moldea