Sadly, I think the question just got answered:
Moscow attack: Did Russia ignore US 'extremist' attacks warning?
The 7 March warning from the US to its own citizens was unusually specific. It talked of reports that "extremists" had "imminent plans to target large gatherings in Moscow" and specifically mentioned concerts. It advised Americans in the city to avoid large gatherings over the coming 48 hours.
The timing may not quite match, but other details do tally closely with events on 22 March. It seems clear Washington had some kind of intelligence and that it related to Islamic State (IS) - the group that has issued a statement saying it was behind the Moscow attack.
F...ing nutcase ISIS. Just like Bataclan. Condolences.
The US supposedly warned Iran about the attack ISIS carried out at the Soleimani memorial on Jan 3, 2024, which killed 84.
CNN
“Prior to ISIS’ terrorist attack on January 3, 2024, in Kerman, Iran, the US government provided Iran with a private warning that there was a terrorist threat within Iranian borders,” the official said. “The US government followed a longstanding ‘duty to warn’ policy that has been implemented across administrations to warn governments against potential lethal threats. We provide these warnings in part because we do not want to see innocent lives lost in terror attacks.”
The Iranian government was ultimately unable to stop the ISIS attack, which was the deadliest in Iran since its 1979 revolution. At least 84 people were killed and 284 injured in the blasts on January 3, which hit near Soleimani’s burial site in southern Iran. ISIS claimed responsibility for the attack one day later.
(That said, one also needs to remember that anti-terrorism watchers probably get a lot of false alarms and leads that never pan out. It is is a well-known human tendency to over-weigh low occurrence prediction "matches" in while ignoring all those that fall through. That's what helps horoscope writers to make bank). So being told doesn't automatically mean: should have caught it.