The difficulty would indeed adjust to factor the new hash - and if you were someone still trying to use more energy on older, less efficient, miners, you'll be left in the dust comparatively, even if you're still consuming more energy than others using the more efficient miners.

Energy and hashrate are definitely NOT unconnected, it's just that they're not connected at a fixed 1:1 ratio. The efficiency of the hashrate production is the abstraction between Bitcoin and the energy used to mine.