During his foreign service career, Kornblum specialized in European and east–west relations and played a defining role in many of the important events leading up to the end of the Cold War.

These included the Quadripartite negotiations on Berlin (1970–1973), the Helsinki Final Act (1973–1975), the Belgrade Conference of the Organization for Security and Co-operation in Europe (OSCE) from 1977 to 1978, the stationing of [intermediate] nuclear weapons in Europe (INF) in the 1980s, U.S. President Ronald Reagan's historic 1987 appearance at the Brandenburg Gate in Berlin, German reunification (1990), the Helsinki Summit Conference of the OSCE (1992), the Dayton Agreement on the Balkans (1995), enlargement of NATO (1997), the post-Cold War security settlement with Russia and Ukraine and the agreement on compensation of slave laborers and establishment of the Reconciliation Foundation of German Industry (2000).

Kornblum conceived and organized the event and worked for more than a year to gain acceptance for political initiatives which included the famous "tear down this wall" phrase in the President's speech.

It was conceived by Kornblum and his team as a memorable slogan for a broader American initiative to remind both East and West that the United States was not willing to accept an undemocratic status quo in the center of Europe.

Kornblum's article goes on to describe the many political pressures exerted in Germany and Washington as this initiative was being implemented and concludes with reflections on the significance of the speech from a perspective 20 years later.

Heightened United States security requirements led to a long and at times bitter dispute with Berlin authorities during which Kornblum became the target of repeated political and public criticism.

After leaving diplomatic service, Kornblum pursued parallel career tracks in business, consulting, and political commentary in Europe and the United States.

He was a member of the advisory councils of Russell Reynolds[2] and Consultum AG,[3] and an advisor to the Finnish Innovation Fund SITRA and to the Center for Strategic and International Studies in Washington.

During the last ten years of his life, Kornblum established a strong public voice defining the implications for Europe and the United States of the new era in global politics which followed the end of the Cold War.

He built on both his diplomatic and business experience to focus particularly on the issues connected with the rapidly changing relationships between government and the private sector in a globally integrated world.

Looking to the future of the Atlantic world, Kornblum presented his vision for the evolution of Germany and Europe in an article published in the November/December 2009 issue of the conservative political journal The American Interest.

Here he argued that the end of Cold War confrontation and spread of free market systems made possible the establishment of a tight web of open-sourced networks which overcome traditional geography and create new patterns of culture and trade.

Kornblum suggested that increasing global integration would gradually reduce Germany's fear of being caught in the middle of big power confrontation and give it a new sense of confidence.

Kornblum expanded his commentary on the Obama era in the book Mission Amerika (2009), written in German together with well-known television commentator Dieter Kronzucker.