The whirlwind of summits across Europe this week by US president Joe Biden is designed to relaunch the transatlantic alliance after the damaging Trump years.
Two US summits in Brussels, with Nato and with the EU, on the back of a meeting of the G7 major economies in Cornwall, are about solidifying a common front and reassuring Europe that "the United States is back" at a time when the West sees increasing challenges from Russia and China.
Moscow and Beijing are both blamed for cyberattacks, disinformation and increasing assertiveness on their borders, from Russia's occupation of part of Ukraine, to China's tightening grip on Hong Kong.
But a number of telling moments during the trip have revealed areas of enduring disagreement within the club.
Britain’s reluctance and refusal to update an IT system, hire border staff, build customs posts and implement agreed checks in Northern Ireland managed to hijack a hoped-for show of unity by the G7 in Cornwall.
Traditional alliances
Prime minister Boris Johnson only further dug in on the issue despite combined pressure from the EU and US. It indicates he is not finished exploiting the matter for domestic political purposes, and that contrary to the hopes of Washington, the Brexit-related tensions that have been toxic to traditional alliances in recent years can still not be consigned to the past.
In the EU, not all member states are fully convinced by the US return to the stage. “America First” policies were driven by the US electorate, and there is no guarantee against a repeat in four years’ time. Some EU leaders emphasise it must pursue its own interests autonomously.
"The last years have also made clear that we Europeans should get out of the shadows of the US and have our own clear priorities," Belgian prime minister Alexander De Croo said after the Nato summit.
Trade and tax
While the US has pushed for a tougher stance on China, some in the EU prefer a "middle way", stressing trade ties and China's importance in tackling climate change. Both French president Emmanuel Macron and German chancellor Angela Merkel played down the issue of China after a Nato declaration described "challenges" from Beijing, including its build-up of nuclear warheads.
Two key commissioners are due to meet with Biden on Tuesday. One is Valdis Dombrovskis, the trade commissioner, reflecting the work ahead for the two sides to unwind the trade disputes that worsened during the Trump presidency. The other is Margrethe Vestager, the EU's competition czar, who has led a charge to rein in the excesses of tech giants which are largely US multinational companies.
These policy issues will be the clearest test of whether the transatlantic alliance is truly “back”: whether the US and EU can succeed in agreeing on multinational taxation and digital reforms and the permanent dropping of tariffs.