ExplainerWill US-UK begin a fresh chapter as new PM Liz Truss and King Charles III settle in?

President Joe Biden headed to the United Kingdom on Saturday to pay his respects to Queen Elizabeth at a time of transition in US-UK relations, as both a new royal and a new prime minister are settling in.

The hawkish approach of Prime Minister Liz Truss to Russia and China puts her on the same page as Biden. But the rise of Truss, 47, who once called the US-UK relationship “special but not exclusive,” could mark a decidedly new chapter in the transatlantic partnership on trade and more.

Of high concern for Biden officials in the early going of Truss’s premiership is her backing of legislation that would shred parts of the post-Brexit trading arrangements in Northern Ireland. Analysts say the move could cause deep strain between the UK and the European Union, and undermine peace in Northern Ireland. White House press secretary Karine Jean-Pierre said the move “would not create a conducive environment” for crafting a long-awaited US-UK trade deal coveted by Truss and her Conservative Party.

“She’s signalled that she’s willing to go to the mattresses on this and that’s going to cause a rift not just between the UK and EU, but the UK and the US,” said Max Bergmann, director of the Europe programme at the Centre for Strategic and International Studies in Washington and a former senior State Department official in the Obama administration. “It’s one that’s going to keep the White House up at night.”

The two close allies now find themselves in a period of political uncertainty on both sides of the Atlantic. Not unlike his fellow septuagenarian Biden, King Charles III faces questions from the public about whether his age will limit his ability to faithfully carry out the duties of the monarch.