Are American Teachers trained on how to deal with ADHD and other "special" needs children in NORMAL public schools?

Public schools usually have special education. I believe you need to major in Special Education in college in order to teach special education classes. Special education teachers can handle a variety of situations because they need to be able to handle their students since they have different needs. Most American teachers are most likely not trained to deal with Special needs students because they get frustrated easily (especially high school teachers).

I have just gone through many college classes in order to get a BA in art education, K.-12. And yes, I was told that 12% of my students would be special needs, including gifted and talented in that category. And, yes, in my arts courses they covered topics such as how to enrich the experiences of the challenged children/teens in the art classroom, and I am sure they do the same for any specialty, be it pre-k, or elementary education, or whatever. Now, when you say "deal", ah, there's the rub. No 2 children or teens are exactly alike and there is in no way any way to teach people how to deal with every single situation that might come up. Or even to imagine those situations. Having a child of mine, now grown, with autism, ADD, OCD, Tourette's and more (as well as having found out in my 40s I was autistic myself), I can tell you this with total certainty. Remember, teachers are human, too, and one should grant them the same understanding you may want all these teachers to have towards all their students. If I presume too much I apologize. BTW, there is no such thing, in my mind, as "normal" school, unless you are talking about historical or other scholastic nomenclature. Perhaps you meant REGULAR. As in, not special at all.

Yes, American public schools legally cannot block children with disabilities from enrolling in classes.

High school teachers are included in this. Getting frustrated easily is not a valid excuse. The parents/guardians and even student can initiate legal action if the teacher behaves inappropriately because of the student's disability. It is illegal under federal law to single out a student.

The teacher would need to find another profession if they get frustrated in the workplace and are lashing out at the student including a student with disabilities. Like any other workplace, it is their responsibility to behave according to the terms of an employment contract.

Yes to an extent. In my elementary ed classes, they taught about disabilities and how to work with them and we even had to include accommodations on our lesson plans for children with disabilities. Granted it's not to the same extent that a special education teacher would learn about it.