That is not an Employment Agreement. It is a letter offering you the position and it states that the company can modify (change) the terms at any time,
You have two steps which you should take together:
1. Ask the General Counsel to meet privately with you. Tell the General Counsel that you do not appreciate being shown such disrespect whether in front of executives at a large meeting or in private. That you expect to be shown the respect which you also give. And, that if this happens again, you fill file a formal Complaint with management and take whatever steps are necessary to insure that you receive the respect which you deserve;
2. Speak to your immediate boss in private and ask him why he did not say anything when you were spoken to this way at the meeting and embarassed in front of all the other executives. Tell him also that if this happens again, you will file a formal Complaint with the Equal Employment Opportunity Commission ("EEOC") in the company's home State in the US.
The EEOC is responsible for taking all Complaints based on Hostile Work Environments and Discrimination, and investigating them. Once they complete their investigation, they issue a "Right to Sue" letter to the employee, giving the employee the right to sue the employer for damages. The employer cannot take any action against the employee in retaliation for filing any Complaint with the EEOC and if it does, the employer must pay heavy fines and penalties. The EEOC has defined a "Hostile Work Environment" as one where an employee or employees do or say things to another employee and make it difficult and almost impossible for the employee (You) to perform the duties and responsibilities of their position.
Of course, you will say these things to your boss in a respectful way, but also in a way that he understands that you will not tolerate this treatment again. This should be enough to let everyone know you mean what you say and should silence them and show you the respect that you deserve. Remember, regardless of where you work, it is a US company and the policies of the company on how employees are treated are subject to the laws of the US and the laws of the home State of the Company.
I wish you the very best,
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