Green served as president of the International Republican Institute[1] from 2014 to 2017 and sits on the board of directors of the Millennium Challenge Corporation.

In 1992, Green was elected to the Wisconsin State Assembly, where he served District 4 for six years and rose to the position of chairman of the Republican Caucus.

[15] While a U.S. Representative, Green was a member of the House Judiciary Committee, vice chair of the Crime, Terrorism and Homeland Security Subcommittee, and co-founded the bipartisan Faith-Based Caucus.

Then-Milwaukee County Executive Scott Walker dropped out of the GOP primary on March 24, 2006, citing a lack of campaign funds (he would later win the governorship in 2010).

On June 8, 2007, President George W. Bush announced Green's nomination as United States Ambassador to Tanzania.

Senator Chris Dodd, a member of the Senate Foreign Relations Committee, put a hold on Green's nomination to replace Michael Retzer as ambassador, citing Retzer's action of revoking the country clearance of Peace Corps Country Director Christine Djondo as interference in the independence of the Peace Corps.

During his tenure, Green helped craft the Millennium Challenge Act, which expanded America's commitment to invest in developing nations that are pursuing political and economic reforms.

USGLC is a foreign policy foundation that describes itself as "a broad-based influential network of over 500 businesses and NGOs; national security and foreign policy experts; and business, faith-based, academic, military, and community leaders in all 50 states who support strategic investments to elevate development and diplomacy alongside defense in order to build a better, safer world".

[27] He served as president and CEO of Initiative for Global Development, a nonprofit organization aimed at reducing world poverty, from 2013 to 2014.

[28] From 2014 to 2017,[29] Green served as president of the International Republican Institute (IRI), an NGO chaired by Arizona Sen. John McCain.

[30] In May 2017, Green was nominated by President Donald Trump to lead the United States Agency for International Development.

His nomination was backed by aid organizations and politicians, with The Guardian writing that Green "is well regarded and known for his bipartisan approach to foreign assistance".