How Does a Block header’S Merkle Root Relate to the Immutability of the Block’s Transaction Data?

The Merkle Root is a single hash representing all transactions in the block. Any change, even a single bit, to any transaction would change its hash, which would cascade up the tree, resulting in a completely different Merkle Root.

Since the Merkle Root is included in the block header, altering transaction data would invalidate the entire block and all subsequent blocks. This cryptographic linkage enforces immutability.