Americans reserve the right to back out of an agreement at any time during its early stages. This sounds like a contradiction in terms, in the sense that once an agreement has been made, one should keep their word.
It is not. American agreements in their early stages are agreements in the making, they are under consideration, are conditional. Americans will do their best to deliver what they have agreed to, if they can, are permitted to, if time and resources enable them.
To go into too much detail of an agreement up front is a potential waste of time and effort. Americans want first the very basics of the agreement, in order to quickly assess whether they can and want to enter into it.
If the initial response is positive, they will enter further into the agreement, taking in more details, proceeding if they can, are permitted to, if time and resources enable them.
It is a step by step process, and not an all or nothing decision.