First, two weeks ago, came television images of a dead GI being dragged throughthe streets of Mogadishu by celebrating Somalis, after a bloody battle between US Rangers and the forces of General Mohamed Farah Aideed.
Then, on Tuesday, came the extraordinary spectacle of a US Navy ship, carrying 200 US and Canadian peace-keeping personnel to Haiti, being stared down by a mob on the docks of Port-au-Prince, then turning around and sailing, ingloriously, back to base.
No one, least of all President Bill Clinton, should be surprised at the disenchantment expressed here in Cincinnati, Ohio. This is heartland America, and the voices heard here represent the uncertain mood of the whole country.
There has always been a tinge of isolationism in Cincinnati, dating from the days when Senator Robert Taft, son of President William Taft and a city icon, headed the isolationist movement in the Republican Party before and after the Second World War.
'I'd be glad to give help to people who need it and want it,' says Cincinnati butcher Bob Eckerlin. 'But people who need it but don't want it - well, to hell with them. We should stay the hell out.' He is talking specifically about Haiti and Somalia, where he believes America is not welcome and therefore can do little good.
The dawn rush in Cincinnati's 160-year-old Findlay Market is over and Mr Eckerlin, 64, is scooping mince out of a plastic pan with his hands and moulding it into fresh dumpling-size servings for sale.
Mr Eckerlin's sentiments are shared down the length of the high-roofed structure, a landmark in the city's Over-the- Rhine neighbourhood, once a well-to-do district of German immigrants and now a slum with an overwhelmingly black population. The butchers, though, have stayed on, and almost all have Germanic names. They sell mostly pigmeat, and are a reminder of Cincinnati's halcyon sausage-making days when it was known around the world as Porkopolis.
Fred Mueller, 59, whose stall is the other side of the aisle from Mr Eckerlin's, also advocates US withdrawal from Somalia, but not before revenge has been exacted for the US soldiers killed there. 'Anyone who takes an American soldier's life in peacetime should be lined up against a wall and shot,' he growls, laying out huge pink chops. 'You feed them food, then they shoot you - that's bad.'
At the other end of the market, Alice Geiger, 63, who has worked her meat stall for 30 years, offers an observation, repeated many times by others interviewed here and around the city: 'We should get out, because America has to pay attention to its own first. There are sad stories here, too, and a lot of people who need help.' Mrs Geiger does her own bit to help the local poor: every evening she delivers left-over cuts to the local soup kitchen.
The first display of public impatience came after the Mogadishu debacle, when voters in their thousands telephoned members in Congress, demanding an immediate withdrawal from Somalia. The cry was faithfully relayed by Congress to Mr Clinton, who has had to tailor policy accordingly.
Although he almost defiantly ordered that the US force be more than doubled, Mr Clinton has also pledged to bring all the soldiers home by next April at the latest, and has halted the UN-inspired manhunt for General Aideed.
In such an atmosphere it is not surprisingthat the President has resisted the temptation to respond with force to the renewed violence in Haiti - marked by the assassination on Thursday of the interim government's Justice Minister, Guy Malary - or to the apparent betrayal by Haiti's military of the UN-brokered accord to reinstate deposed President Father Jean-Bertrand Aristide.
That there has been no popular clamour for the Haitians to be taught a lesson for displaying such insolence towards the world's last superpower is as good an illustration as any of the new mood in the country. Here in Findlay Market at least, the meat vendors mostly approve of President Clinton's decision to withdraw the navy last Tuesday, and to opt for a renewed programme of economic sanctions against Haiti. If he had been the ship's captain, Mr Eckerlin says, he would have 'said thank you very much, thumbed my nose at those people and just steamed right on by'.
But how far this distaste for military engagement in Somalia and Haiti reflects a general shift towards US withdrawal from international affairs, and even isolationism, is a question yet to be answered - though it is tempting to believe it is a trend already well advanced.
A poll conducted last week by ABC TV News suggested that only 22 per cent of Americans believe that the US should play a 'leading role' in world affairs, and 74 per cent said the US should reduce its involvement considerably.
In Washington, it has become a truism that events in Somalia and Haiti will make it impossible for Mr Clinton to recommend to Congress the deployment of US troops to Bosnia, should they be needed for a peace-keeping role.
One echo of the isolationist arguments of the late Robert Taft, who opposed the war against Hitler, is providedby his son, also Robert Taft, a former senator himself and now the head partner in a Cincinnati law firm. Although he used to disagree with his father's position, he admits that of late he has been tending towards it.
'We have made a lot of errors of judgementof late,' he suggested in an interview, warning against further involvement in Somalia or Haiti. 'I'm very wary of US involvement in developing nations. We can't forcibly democratise them. It's unrealistic, as anyone who has been to Africa will know. They talk about clans in Somalia but they're really tribes.'
And he congratulated Mr Clinton on steering clear of conflict in Haiti. 'His decision to hold up was perfectly correct. Sending in armed personnel would probably result in our taking it over. I think most Americans think that it was a sound decision.'
And yet in Cincinnati, it is hard to find anyone willing to make the isolationist case outright. The implication of Mr Eckerlin's comments is that America should remain willing to intervene abroad, but only where it is wanted by the majority of the population concerned, and where there is reasonable hope that it can do good.
In different ways, that more selective attitude is expressed by many in the city. 'If a country asks for it, that's OK,' suggests Brian Doyle, a photographer, who with scores of office workers was resting during the Thursday lunch-hour in Fountain Square, Cincinnati's focal spot. 'But I have to question just sending troops for the sake of sending troops. Mind you, if it is an ally asking for help, then the US should certainly consider it.'
David Learned, 39, a telecommunications technician, had similar ideas. 'I see nothing wrong with us getting involved in countries that are really democratic civilisations. But if it's a country that doesn't want the American form of democracy, then I don't think we should get in the middle of it.'
Asked whether America, as the last superpower, had an obligation to mind the rest of the world, he said: 'If we believe in a cause, Americans have always been willing to fight for things. It's not so much a question of obligation, but more of a willingness. A lot of people are willing to fight for democracy and freedom when it is in jeopardy, but we have to be clear whether it is really worth it.'
Americans may be becoming more sceptical of foreign adventures of the kind that Ronald Reagan and George Bush pursued. No grand gestures of the Libya-bombing ilk are expected of Mr Clinton. But there is no evidence yet that they are really on the path to isolationism. Surely Americans are too patriotic and too conscious of international prestige for that.