As they stand, the requirements for the 4 are below (and they must be triggered sequentially):-
Triggers when either:-
* USA is attacking, or under attack from, either Germany, Italy or Japan
* The Axis have 312 VPs with Italy & Japan in the Axis
* The Axis have 271 VPs with Japan in the Axis
* The Axis have 236 VPs with Italy in the Axis
* The Axis have 195 VPs with neither Italy & Japan in the Axis
* The Comintern have 147 VPs
* Germany's belligerence is 35
* Italy's belligerence is 40
* Japan's belligerence is 40
* the UK is at war with the USSR (this could be very gamey...)
* the USSR is allied to either Germany or Japan
* Germany is allied to Japan
* China is annexed or a Japanese puppet
* Japan controls Chongqing
* Either Paris, London, Moscow, Rome or Berlin has fallen
* Brussels has fallen and Italy is in the Axis
* any part of the Americas, Iceland, Greenland is in Axis control somehow
* Azores have fallen, or Portugal is allied to Soviets, Germans, Italians or Japanese
The event gives the USA:-
* -1 professional army
* +3 factories in Chicago
* +5% peacetime IC modifier
* +3 hawk lobby
* +50 manpower
Event 2
Triggers when either:-
* USA is attacking, or under attack from, either Germany, Italy or Japan
* The Axis have 362 VPs with Italy & Japan in the Axis
* The Axis have 321 VPs with Japan in the Axis
* The Axis have 286 VPs with Italy in the Axis
* The Axis have 245 VPs with neither Italy & Japan in the Axis
* The Comintern have 197 VPs
* Germany's belligerence is 50
* Italy's belligerence is 50
* Japan's belligerence is 50
* the UK is at war with the USSR (this could be very gamey...)
* Japan is at war with either the UK, Netherlands or USSR (needs the first event to trigger beforehand, somewhat gamey)
* the USSR is allied to either Germany or Japan
* Germany is allied to Japan
* China is annexed or a Japanese puppet
* Japan controls Chongqing
* Either Paris, London, or Moscow has fallen
* any part of the Americas, Iceland, Greenland is in Axis control somehow
* Azores have fallen, or Portugal is allied to Soviets, Germans, Italians or Japanese
The event gives the USA:-
* -1 professional army
* +1 interventionism
* +3 factories in Chicago
* +10% peacetime IC modifier
* +1 hawk lobby
* +75 manpower
Event 3
Triggers when either:-
* USA is attacking, or under attack from, either Germany, Italy or Japan
* The Axis have 412 VPs with Italy & Japan in the Axis
* The Axis have 371 VPs with Japan in the Axis
* The Axis have 336 VPs with Italy in the Axis
* The Axis have 295 VPs with neither Italy & Japan in the Axis
* The Comintern have 247 VPs
* Germany's belligerence is 60
* Italy's belligerence is 70
* Japan's belligerence is 70
* Japan is at war with Netherlands or England (provided Japan is the aggressor)
* the USSR is allied to either Germany or Japan
* Germany is allied to Japan
* China is annexed or a Japanese puppet
* Japan controls Chongqing
* Either London or Moscow has fallen
* any part of the Americas, Iceland, Greenland is in Axis control somehow
* Azores have fallen, or Portugal is allied to Soviets, Germans, Italians or Japanese
The event gives the USA:-
* -1 professional army
* +3 factories in Chicago
* +10% peacetime IC modifier
* +1 hawk lobby
* +100 manpower
Event 4
Triggers when either:-
* USA is attacking, or under attack from, either Germany, Italy or Japan
* The Axis have 462 VPs with Italy & Japan in the Axis
* The Axis have 421 VPs with Japan in the Axis
* The Axis have 386 VPs with Italy in the Axis
* The Axis have 345 VPs with neither Italy & Japan in the Axis
* The Comintern have 297 VPs
* Germany's belligerence is 90
* Italy's belligerence is 100
* Japan's belligerence is 100
* the USSR is allied to Japan
* Germany is allied to Japan
* Japan is at war with Netherlands or England (provided Japan is the aggressor)
* any part of the Americas, Iceland, Greenland is in Axis control somehow
* Azores have fallen, or Portugal is allied to Soviets, Germans, Italians or Japanese
The event gives the USA:-
* +1 interventionism
* +50% peacetime IC modifier
* +1 hawk lobby
* +525 manpower
Chongqing should not be an all or nothing city, and there are plenty of other balancing triggers that make the US gearing quite favourable towards the Allies.
Admittedly the VP requirements are likely off too, as I think they use vanilla VP values, but I think the other criterions are satisfactory.
Also, for the China surrender event, China needs to lose 90% of its VPs and have lost Nanjing and Chongqing, I'd suggest reducing this to 65% of its VPs or 65% of its national territory - bear in mind it would still need to lose Nanjing and Chongqing.