I think this view us a overly flattering interpretation of events.
The basic facts is that the US did give serveral verbal promises that NATO wouldn't expand, and that the later written treaties did not make such promises.
It is however not clear at all from the evidence that the US ever said that they were retracting the early verbal promises.
Further the Brookings piece you linked is trying to make hay out of the fact that the verbal promises were explicitly "only" about expansion into Eastern Germany, which is really just childish: If someone says you can't borrow their shovel, that's not to be understood as them allowing you to borrow anything else they own without asking.
The point is that while it's true that the US never signed anything that prohibited NATO expansion to the east, they were aware they did at one point promise just that.
Then later, as the US changed its minds during spring of 1990, the strategy seems to have been to just pretend not to remember those earlier promises and by narrowly focusing on German unification hope that the issue of the wider European order didn't come up again.
One thing that is really remarkable with all these accounts of how there wasn't any pledges is that the talks were only about German unification in the most narrow sense, and nothing else happened. So the Ion Curtain fell but the US was apparently entirely uninterested in talking to the Soviets about what the new overall structure would be?!
Independently of your overall point, what strikes me here is that Trump could not possibly care less about any promises that the "US" may have made. He is effectively breaking every deal ever made, with no regard for any continuity of policy (not just now, think the Iran deal in his first term). With Zelensky yesterday, he again went on about this ceasefire deal would be with "him", not like "the other presidents".
In this context, its a bit rich for the pro-Trump "great peace negotiator" group to imply that the US needed to keep verbal promises made 35 years ago. It was, after all, just what some dude said one time.
He's maybe breaking continuity of the US as a whole, but in general he seems to be quite consistent in his actions and motivations. And maybe he's the first president in a long time that actually understands Russia's perspective.
From the last presidents he's the one that started the least wars. I don't understand why people are saying that he's pairing with Russia when he wants to end a war that's been going on for 3 years.
The basic facts is that the US did give serveral verbal promises that NATO wouldn't expand, and that the later written treaties did not make such promises.
It is however not clear at all from the evidence that the US ever said that they were retracting the early verbal promises.
Further the Brookings piece you linked is trying to make hay out of the fact that the verbal promises were explicitly "only" about expansion into Eastern Germany, which is really just childish: If someone says you can't borrow their shovel, that's not to be understood as them allowing you to borrow anything else they own without asking.
The point is that while it's true that the US never signed anything that prohibited NATO expansion to the east, they were aware they did at one point promise just that.
Then later, as the US changed its minds during spring of 1990, the strategy seems to have been to just pretend not to remember those earlier promises and by narrowly focusing on German unification hope that the issue of the wider European order didn't come up again.
One thing that is really remarkable with all these accounts of how there wasn't any pledges is that the talks were only about German unification in the most narrow sense, and nothing else happened. So the Ion Curtain fell but the US was apparently entirely uninterested in talking to the Soviets about what the new overall structure would be?!