Undermine vs. destroy might be a distinction without a difference but I still think Obunghole is MUCH worse than Carter. Obunghole WANTS to destroy America while Carter's ineptness, naive foreign policy, and irrational hatred for G.W. Bush have unintentionally allowed our enemies to advance against us. (How's that for a run on sentence?)
Obunghole is the first POTUS in my lifetime that I believe sincerely wants what is not good for America. Others have acted against us but not purposefully.
I think you got it right.
Carter was bad for the country without him knowing it.
Obama is bad for the country and he KNOWS it.