Yesterday's move came hours after the second firebombing of a car dealership by a hitherto little-known group called Anti-State Action, which prefaced its first attack a week ago with the warning "Welcome Clinton". Instead of a three-day visit starting on Saturday, the president will spend less than 24 hours on Greek soil, after attending a European security summit in Istanbul on November 18 and 19.
The delay, Athens and Washington said, would enable "better planning". In fact it reflects policy differences and resentments which have long simmered between the two countries. These in turn feed into the grievances of a sometimes violent extreme left, which has never forgiven the US for its tacit support of the 1967-74 military junta.
If the public anti-American outbursts of the late Socialist prime minister Andreas Papandreou are no more, many Greeks remain convinced the US is irredeemably biased in favour of arch-rival Turkey in their territorial disputes in the Aegean and over Cyprus.
More recently, many saw a US hand in the affair of the Kurdish leader Abdullah Ocalan, whose capture by Turkish security agents after being sheltered in a Greek embassy was a national humiliation. And this spring Athens was by far the most hostile of Nato members to the Kosovo war and the bombing of the Serbs, its traditional fellow Orthodox allies in the region.
However, despite the latent anti-Americanism, Greece's relations with Turkey are improving for the first time in years and hopes are growing that patient diplomacy by the US might just bring about some movement on Cyprus.
In the end, security worries were the decisive factor in curtailing the Clinton visit. Big demonstrations were guaranteed after the government of Costas Simitis, Mr Papandreou's successor, said it would not block protests at the US embassy or outside the hall where Mr Clinton was scheduled to make a speech. Worse still was the threat of terrorism.
Anti-State Action may be little known, but another far-left group, November 17, has killed 22 people since it emerged in 1975, including five American diplomats and, most recently, the Greek shipowner Constantinos Peratikos, in May 1997.
The group takes its name from the date of a crackdown in 1973 by the military junta on pro-democracy demonstrators at Athens University, an anniversary Mr Clinton will now be avoiding.
Despite its notoriety, and much backstage pressure from Washington for a crackdown, the group has never been brought to account. The failure has fanned suspicion of links with far-left elements within the governing party, and, given Greece's' reputation of being the EU's most dangerous country, a last refuge for the far-left terrorism which flourished in Italy and the then West Germany in the 1970s and 1980s.
The State Department yesterday advised US nationals in Greece to "exercise appropriate caution" during the visit, and to avoid demonstrations. But the Greek Communist Party warned that the delay to the visit would lead only to fiercer protests. "The condemnation of the Clinton visit is a condemnation of US policy towards Greece."