BERLIN — In the preamble to their constitution, the American people pledge to “promote the general welfare and secure the blessings of liberty to ourselves and our posterity.” This compelling, powerful statement has made the United States a world champion of liberty and democracy — a commitment for which all who value and honor the common heritage of freedom are grateful.

It is precisely these values on which the trans-Atlantic partnership was founded. It is not simply a community of interests, but a lasting friendship between democrats and democracies. Although not free of conflicts and by no means perfect, it is a friendship shaped and sustained by the principles of democracy, the rule of law, human rights and a belief in the market economy. We shall never forget that many Americans sacrificed their lives for democracy and freedom in Europe.

However great that legacy may be, sadly, one cannot deny it is in danger of suffering serious damage. The world is undergoing seismic change with barely conceivable consequences. The rules-based international order largely established by the United States and Europe after World War II is no longer automatically accepted by all states. The international system of trade, which for decades has been characterized by the opening up and interaction of markets, is being challenged by a model of barriers and isolationism. A new type of nationalism and authoritarianism is questioning the achievements of freedom and democracy.

This authoritarianism is an external challenge to the Western value-based alliance. Neither Russia nor China has an interest in the joint sustained strength and success of democracies in Europe and the United States. However, our values are also threatened from within. Right-wing and populist parties and movements have gained significant ground in some European countries. Their smear campaigns are poisoning democratic culture and cohesion in Europe.