But the US alert, though less serious than an official advisory not to travel, is an unhelpful overreaction and a kick in the teeth for the European tourist industry.
If intelligence had suggested US citizens were a specific target, the alert might have been justified. But there was nothing in the intelligence reports last week to suggest that.
And the fact that no arrests were made after the report was leaked indicates how nebulous and undeveloped these plots must be.
Yet these sorts of alerts give the damaging impression that Europe is somehow unsafe in general.
The implication is that the continent is made up of weak states such as Pakistan or Yemen which lack the capacity to disrupt these attacks or protect their populations.
The Foreign Office's latest advice is even more misguided, since the UK is surely just as much a target as France or Germany.
What is most distasteful about the US warning, however, is the lack of solidarity it implies.
America is hardly without its own domestic terror threat, as witnessed by the attempted car bombing in Times Square in May. Yet if European governments were to issue a travel alert on America, the US would, understandably, be irritated.
Further, it has been suggested that this latest flurry of activity from terrorists with regard to European targets is a response to the increasing number of US drone attacks in Pakistan. This is a common danger and we surely need to face it together.
Terror threats are, sadly, now a fact of life across the Western world. Governments should, of course, act on specific information and warn their citizens accordingly.
But the issuance of vague and slightly panicked travel alerts merely exacerbates a climate of fear and helps do the terrorists' job for them.
- INDEPENDENT