you are right about the additional layer of needing ratification by US states, but other than that, i see no difference. in the end it's just a name for a specific concept, and the concepts of Grundgesetz and Verfassung are not different enough to argue over which name is correct. i disagree that the difference is the reason why germany named it Grundgesetz. they could have decided to name it Verfassung instead, and nothing would have changed. we would still have the same rules to change it. there is nothing in the name that forces a different approach.

more interesting is the actual contents and the principles that are being covered. debt brake for example in my opinion has no business being part of a constitution or Grundgesetz. it should never have been added there in the first place. that's not what a constitution is for. putting stuff like that in there weakens the Grundgesetz and makes a mockery of it. it reeks of planned economy.

that doesn't mean that the debt brake is bad, or that it should not be protected by requiring a 2/3rd vote to change it. there just should be a different place for that, in order to keep the Grundgesetz focused on issues that you really don't want to change. in other words, even if only a single 2/3rd vote is necessary to approve a change, a change to the Grundgesetz should be a rare exception.