Who from a U.S. MNE is typically involved in an ICAP risk assessment (e.g., level/authority and function)

Typically, a U.S. MNE designates one or two leads to coordinate the MNE’s participation in the ICAP risk assessment. These individuals generally have in-depth knowledge and oversight of the MNE’s international tax and transfer pricing functions. Where necessary, the lead(s) will coordinate with other U.S. tax personnel, local country tax personnel, and/or non-tax business personnel within the MNE as needed.

Sources:
IRM Part 4. Examining Process. Chapter 60. International Procedures. Section 11. International Compliance Assurance Program
U.S. Tax Challenges for Foreign-Based Multinationals