[1] McKinley was born in Caracas, Venezuela, and grew up in Brazil, Mexico, Spain, and the United States.

[5] From 2001 until 2004, McKinley served as Deputy Assistant Secretary in the State Department's Bureau of Population, Refugees, and Migration.

[5] During a tense period of political instability in 2016, McKinley met nearly daily between Afghan President Ashraf Ghani and his coalition partner, Chief Executive Abdullah Abdullah; McKinley acted as a mediator and engaged in shuttle diplomacy to try to preserve the fragile national coalition government and stymie an upsurge in Taliban activity in Afghanistan.

Ambassador, McKinley called upon the Afghan government to conduct a full, transparent investigation into the allegations of Ahmad Ishchi of Jowzjan Province, who in 2016 accused General Abdul Rashid Dostum of abducting and torturing him.

[16][17][18][19] On October 16, 2019, McKinley gave deposition testimony to the House Intelligence, Foreign Affairs, and Oversight committees in the impeachment inquiry against Donald Trump.

[21] McKinley testified that his resignation was prompted in part by the Trump administration's attempted use of U.S. diplomatic missions "to procure negative political information for domestic purposes, combined with the failure I saw in the building to provide support for our professional cadre in a particularly trying time.

"[21] McKinley testified: "I was disturbed by the implication that foreign governments were being approached to procure negative information on political opponents.

[22] Kent provided a memo to McKinley detailing his concerns, which McKinley forwarded to Under Secretary of State for Political Affairs David Hale, acting legal adviser Marik String, and Deputy Secretary of State John J. Sullivan, but received no response.

"[24] McKinley's Pre-revolutionary Caracas: Politics, Economy and Society 1777-1811 (1985),[25] a history of colonial Venezuela, was published by Cambridge University Press and also appeared in a Spanish edition.