Should I file Form 8453 with my Amended US Tax return to the address given in Turbotax instructions or to the address on Form 8453?

Form 8453 is never used with an amended tax return.

 

Form 8453 is a "Transmittal" to mail other forms that cannot be e-filed with an e-filed tax return.   The form 8453 is always mailed with the attachments but ONLY for e-filed tax returns.

 

Since an amended tax return (1040X) CANNOT be e-filed and MUST be mail filed then form 8453 does not apply and no 8453 should be used at all since all necessary forms can be mailed along with the amended return so NOTHING is mailed separately.