My statement does not contravene universal computability since I'm assuming a Turing machine can simulate a human brain.

Well, if you assume that, then you are already most of the way to functionalism, but I suspect we may be talking about different types of simulations.

Let me try another approach: Look at the space-time diagram of a Turing machine adding two numbers and compare with the space-time diagram of a neuron performing a similar summation.

Neurons perform analog summation, so the space-time diagram or causal structure is stochastic/statistical rather than deterministic (addition over real-number distributions rather than digital addition) . My use of the term 'simulation' encompasses probabilistic simulation which entails matching the statistical distribution over state transitions rather than deterministic simulation.

Anything can be simulated imperfectly. Take the weather or C. elegans nervous system.

Neural analog computational systems can be simulated perfectly in a probabilistic sense when you can recreate the exact conditional probability distributions that govern spike events. You can't necessarily predict the exact actions the brain will output (due to noise effects), but you can - in theory - predict actions from the exact correct distribution. At the limits of simulation we can predict exact samples from our multiverse distribution, rather than predict the exact future of our particular (unknowable) branch.

Simulation of intelligent minds is fundamentally different than weather simulation - for the weather we are interested in the exact outcome in our specific universe. That would be comparable to simulating the exact thoughts of a particular human mind in some situation - which in general is computationally intractable (and unimportant for AI).

There are no objective tests for consciousness. Of course you can re-define it in terms of self-awareness but this is not the same.

Science is concerned with objective reality. A definition of consciousness which precludes objective testing is outside the realm of scientific inquiry at best, and pseudo-science at worse.

In common usage the term consciousness refers to objective reality. Sentences of the form " I was conscious of X", or "Y rendered Bob unconscious", or "Perhaps at a subconscious level" all suggest a common meaning involving objectively verifiable computations.

We know that consciousness is the particular mental state arising from various computations coordinated across some hundreds of major brain regions. We know that certain drugs can cause loss of consciousness even while neural activity persists. Consciousness depends on precise synchronized coordination between major brain circuits - a straightforward result of the brain being an hybrid digital/analog computer.

We aren't so far away from being able to objectively detect consciousness via brain scanning and some form of statistical inference - see this interesting work for example (using a clever compressibility or k-complexity perturbation measure).