Could the Supreme Court declare a amendment proposal unconstitutional?

Not quite. I think it’s unlikely the court will ever invalidate an amendment/proposed amendment because of its substance, because my opinion is that the only valid challenge to substance is the Senate entrenchment clause and I think such an amendment is unlikely to be proposed.

As for ruling on the substance of amendment proposals prior to ratification, if a State is not harmed by the proposal itself I doubt whether it could even reach the Court.

Cannot rule an amendment proposal unconstitutional because of its substance, with the single exception I mentioned. I have no qualms with the Court upholding a proposal when challenged on the basis of its substance - with the one exception.

No, it is my opinion.

~Max

One academic argued that constitutional amendments should be considered unconstitutional only if they violate core democratic norms (where I’d argue Article V Senate protection language does not apply) and that these norms must be transnational (ditto).

I’m not claiming that this would fly in the US (where Article V would trounce transnational democratic norms, as would any other aspect of US law as interpreted by the current judicial regime), but I thought it warranted mention.

Hollingsworth v. Virginia