The new Isolationism system works a lot different from the one in GD 1938 v2.
A timer of a sort has been introduced. The timer counts down the number of turns that are left before the United States gets into the war. Now I made this so it would be easy to modify if I got it too long or too short a time period. But basically, if we go by history, this number of turns should be 40. Now nobody is going to wait 40 turns before they play the game, so we have shrunk that down a bit. How much I won't reveal.
So things do not get boring for the United States, they have a number of policies they can enact that either help the democracys, or hurt their opponents. Also we have put in some triggers that will reduce the time the waiting period is, if certain things happen (Like the fall of Paris). Some triggers make things take longer time too (Like the fall of Rome). One of these policies is the Destroyers for bases agreement, that the British will find very nice, in most cases.
Also, one of the things that GD 1938 v2 was guilty of was making the USA simply too strong, when it entered the war. This was because they had no restrictions placed on their economy whatsoever. Well not true now. The US has a economy that is modified according to what level of Isolationism they are under.
Yes, you read right, levels of Isolationism. There are now two levels. The first one is for when war has not been declared by anyone, and the only war is the one between Japan and China. The second one happens the moment war is declared by Germany, Italy, Japan or USSR on USSR (yeah USSR can't DOW itself), France or Britain. This basically amounts to that if the Democracys (or USSR) is at war with the Authoritarian Regimes (I could call the Fascists, but lets not), or USSR.
While they are blissfully asleep, the US is very limited in what they can do. Their economy functions at 40% of what it would be if they were at war. When they do get half awake, because of the noise that the Europeans are making, then they will have 60% of their wartime production.
Now the Lobby Congress card you see above is one that is used to influence Congress. Other nations can influence it too. If a good result for the Democracys is scored, then the counter for when US enters the fray will count down by an extra turn, if a bad result is scored then the counter may not count down at all, and if an average score is made, the turn just goes down by one.
When there is only 5 turns left, everyone will get a message that they are about to enter the war. Now that could happen very fast, or very slow, or maybe never (very unlikely). The fastest it could happen is actually 1 turn (could come about if several things that worry the US happens in the same turn), and as I mentioned never, since the Germans, Italians and Japanese could lobby congress and have it postpone it every turn.