Without a constitutional amendment there’s no guarantee of anything, future congress being bound by past congress is a fundamentally terrible idea. Imagine what

Without a constitutional amendment there’s no guarantee of anything, future congress being bound by past congress is a fundamentally terrible idea. Imagine what the slaveholders in the early 1800s would have tried to do if they could have passed a “slaves forever and nobody can ever change this law” bill (which indeed was what the confederacy tried to do with its constitution). Even then you are subject to future amendments and future courts that interpret that what you really meant by “universal” was only that the government had to pay at least $0.01 to everyone so actually policy X is still universal. There are no “forever guarantees” and indeed that would be awful, the living should never be irrevocably bound by the hand of the dead.