The information appears in table 4 on page 268 of State 2000: A New Model for Managing Foreign Affairs, in a section about US overseas missions. These are listed by size and then, almost as an afterthought, there is a table of 50 countries whose ranking is decided 'by importance to US interests' and in four of which there is no US embassy.
Germany heads the table, followed by France and Britain. The British third place may come as something of a surprise in view of the close alliance with the US in the Gulf war, but France probably finishes ahead because of its pursuit of an independent role within the Western alliance and its economic strength.
China pips Japan for fourth place, presumably because of its military might, independent foreign policy and economic growth. The decline in Moscow's power is reflected in Russia's sixth place. Boris Yeltsin may feel a bit miffed, but it is doubtful if many US politicians think Russia deserves to be higher.
The State Department completed its study in August 1992, before Bill Clinton was elected last year. One surprise is Saudi Arabia's relatively lowly position at 15. This may reflect a belief by US diplomats that Saudi Arabia has no alternative to close alliance with the US. The capacity to cause trouble is presumably responsible for the presence in the top 20 of Iraq, Libya and Cuba, in none of which the US has an embassy. A footnote warns: 'There are some anomalies, eg, 'trouble spots' such as Iraq, whose importance over a long period of time would be diminished.'
By the same token, it is surprising to find that Iran does not occupy a higher place than 38. Under President Clinton, the Iranians are probably being taken more seriously; the US administration is taking a hard line against Teheran as a source of terror and instability in the Middle East.
Finally, the Greek government is unlikely to be impressed at finding itself listed at 31, five places below Turkey. The top 30 in the league table are:
1 Germany; 2 France; 3 Britain; 4 China; 5 Japan; 6 Russia; 7 Mexico; 8 Israel; 9 Canada; 10 Iraq; 11 Italy; 12 Nigeria; 13 Egypt; 14 India; 15 Saudi Arabia; 16 South Africa; 17 Australia; 18 Pakistan; 19 Cuba; 20 Libya; 21 Argentina; 22 Spain; 23 El Salvador; 24 South Korea; 25 Indonesia; 26 Turkey; 27 Thailand; 28 Ethiopia; 29 Syria; 30 Peru.