How do I locate a list of restrictions that would prevent a pilot from flying in the US?
The list is exactly one item long:
Any condition which would impair your ability to conduct the flight safely, and in accordance with FAA Regulations.

Any more specific list will miss things and be riddled with loopholes - at some point we have to trust that pilots are sane and responsible individuals, just like we do when we let people get in a car.



From a medical perspective the general medical certification information page at faa.gov is a good starting point, and the FAA's guidance for Aviation Medical Examiners has lots of details.

There are also some disqualifying conditions which are explicitly listed in the regulations, and a list of (some of the) medications which will prevent the FAA from issuing a medical certificate.



The things I noted above will prevent you from getting a medical certificate.  Once you HAVE that certificate the "I'M SAFE" checklist or something equivalent expands upon that and tries to help pilots determine whether they're fit to fly right at this moment. There are various ways of interpreting the acronym, but a common one is:

I for Illness
Do I have an illness or any symptoms of an illness?

M for Medication
Have I been taking prescription or over-the-counter drugs?
If so, do they have a negative affect on my ability to perform this flight?
Are any of them disallowed by the FAA? 

S for Stress
Am I under psychological pressure from the job or personal issues?

A for Alcohol
Have I been drinking within eight hours? Within 24 hours?

F for Fatigue
Am I tired and not adequately rested?

E for Eating
Am I adequately nourished, or at least "not hungry"?