Any of these things happen in the time interval from the title:

• A constitutional amendment is passed and adopted in the USA

• There is an emergency presidential succession. IE vp or someone else suddenly becomes president outside of the normal schedule in the USA

• A nuclear weapon explodes in the USA of at least 50 kilotons

• A disaster strikes killing at least 10k people in basically one shot, anywhere in the world. Diseases count, quakes, volcanos etc. Manmade and natural. A disease which kills more and more til the amount is reached. Or a meteor which knocks out that many people. Note that side-effects don't count. i.e. a meteor which kills 2k people but which also leads to a major war 3 months later in which many more die, wouldn't count. They have to be killed by the thing. Similarly if the meteor knocks out power and then gradually due to power loss they die, that doesn't count. But, if the meteor knocks out a dam and the water hits them, then that would count.

• An attack by a terrorist or nation or individual kills at least 3k people in the USA

• $collapse means the inflation rate is greater than 100% annualized for at least a month in the USA