In what way(s) does the Catechism of the Catholic Church undermine anything taught in the Baltimore Catechism or the Catechism of Trent?
It's not so much an undermining and it is an obliteration. When you have catechism teachers (some who have posted here) having to sneak Trent and Baltimore into their classes for fear of being discovered, something stinks.
And let's face it, JP's catechism while not purosely or outwardly undermining the former, is the "new Catholic lite" version. His singular mind simply was incapable of producing anything comparable to the depth, wisdom and intelligence of those that existed.