Aside from the swarm of black American-made police cars sheltering under the shade trees from the 100-degree noonday heat, a idle traveler would find nothing amiss at the now-ruined Osirak nuclear reactor complex.

Just as before last Sunday's Israeli raid, the same 100-foot-high horseshoe-shaped earthworks protect the nuclear facility 12 miles southeast from the Iraqi capital by superhighway.

So, too, do the antiaircraft guns and their probing radar dishes, and short-range surface-to-air missiles visible from the road -- and doubtless the heavier missile systems out of sight beyond the earthworks.

Indeed, the refinery and military camp halfway into Baghdad along the same road are even guarded by 21 orange barrage balloons -- throwbacks to World War II days.

If all this smacks of shutting the barn door after the horse has bolted, President Saddam Hussein's government here is playing a defiantly upbeat tune.

The official Iraqi News Agency today seized on the world condemnation of the Israeli raid as proof of "consolidation of Iraq's fame" -- rather than its humiliation -- "and the further isolation of the racist and aggressive Zionist entity," as the Jewish state is called here.

The Arab world has been accustomed to the alchemy of changing defeat into victory since the late president Nassar's masterful recovery from Egypt's 1967 military catastrophe at Israel's hands.

The reasons for striking such an optimistic note are subtle and crass at the same time.

Bogged down since last September in a war against Iran, the president is using the Israeli raid to rally support from the entire Arab world.

All Arab countries sent delegates to the one-day Arab League foreign minister's meeting here yesterday with the exception of Egypt, which denounced the Israeli raid in terms as strong as, if not stronger than, those represented here.

Even archenemies Libya and Syria, which support Iran in the Persian Gulf war, felt compelled to be represented here although at less than full ministerial level.

Non-Arab countries have condemned the Israelis, whose image here, unlike in most Arab nations, remains that of the Middle East superman yet unscathed by the 1973 Arab-Israeli war.

Residents here argue that the Persian Gulf War has conditioned Iraqis to the vulnerability of their capital and country to air attack, so that the Osirak reactor complex raid was more easily accepted than might have been expected.

Since the raid, various leaders of the government and the ruling Arab Baath Socialist Party have said Iraq was determined to push ahead with its nuclear program although diplomats here suspect not in the near future.

Despite Israeli Prime Minister Menachem Begin's insistence that the Iraqis had threatened to use a nuclear bomb against Israel, diplomats scouring through mounds of official pronouncements have found no such evidence. s

Basking in what they imagine may be long-term worlwide sympathy, Iraqi leaders are coldly plotting a course of action designed to embarras the United States in its dealings with Israel.

Diplomats here credit Iraq with sufficient realism and knowledge of American commitments to the Jewish state to know that Washington is unlikely to do more than delay arms shipments to Israel.

And Iraq's relations with the United States have improved just enough in the past year -- without formal resumption of diplomatic ties broken since the 1967 Arab-Israeli war -- to warrant "testing" the Reagan administration rather than insulting it outright.

Important, but not necessarily crucial in this reckoning, is how the United States will vote in the current United Nations Security Council debate on whether to condemn the Israeli raid.

"Iraq wants something to show that the United States is not automatically tied to Israel's position," a Western diplomat remarked. "Some credible truth that would damage America's ties with Israel so Baghdad can say that the relationship will never be the same."

And if contemporary Iraqi history under Baath Party leadership is any yardstick, the government will take revenge even though it has few ways of striking militarily against Israel.

"Yes, they want revenge," a Western diplomat said. "Eventually . . . . [but] They can wait. They do not want to get suckered into something as stupid as hitting Israel blindly. Why should they ruin their morally good position by doing something childish for minimal damage? They are cool characters, not like Libya's Muammar Quaddafi, who urged bombing the Israeli nuclear center at Dimona."