President Biden faces tremendous challenges to overcome political polarisation as he re-commits the United States to the Paris Agreement on Climate Change and promises decarbonisation of the US economy over the next three decades. To achieve deep decarbonisation, recent scholarship identifies the crucial role of broad policy mixes that create reinforcing effects between climate and energy policies to trigger technological innovation, restrict polluting activities, promote green growth, and ensure just energy transitions. Drawing on this literature, the article explores the conditions for developing such policy mixes in the US context in three policy phases. How and why have key policy conditions developed differently in the climate- and energy policy fields, and to what effect for decarbonisation policies? The analysis shows that growing political polarisation blocked bipartisan agreement, produced negative policy feedback, and caused instability in the climate policy field, whereas these mechanisms did not dominate the energy policy field. A more bipartisan approach to renewable energy policy allowed long-term experience and positive feedback in energy-policy programmes that helped to trigger technology innovation and subsequent GHG emissions cuts. Different policy conditions within these policy fields discouraged a coupling between them that could have facilitated green-growth policies. The economic shock caused by the coronavirus pandemic may potentially change policy conditions and build a path to deep US decarbonisation in the future, but only if political polarisation on climate change can be overcome.