All of them are US personal accounts in my name.
Their first response was
I'd like you to know that your Rewards program with BlueSky from American Express Card account cannot be linked with your Membership Rewards program for your other two Card products.I'd like to clarify that BlueSky Rewards program and Membership Rewards program are two separate programs.
They keep referring to them as "BlueSky Rewards" which is frustrating as they are clearly called Membership Rewards Express. The second response simply told me what I could use my "BlueSky Rewards" for.