... and since I am at it, did anyone consider the guarantees to be set 
in place so that the USA government does not decide to reverse the 
process at a certain point in time, after the conclusion of the 
transition, and take it over again?

This could happen if the post-transition dynamics leads to new 
arrangements which the US government does not like, or if a change in 
the US government might lead to a full review of the process.

How secure this will be after its conclusion?

fraternal regards

--c.a.