There was snow on the ground in northern EstoniaOne of the Baltic States. It was taken over by the Soviet Union during World War Two but regained its independence in 1991. on Sunday as the huge AntonovThe world's largest aeroplane, used by both the Ukrainian and the Russian air forces. AN-124 took off for Ukraine. On board were rifles, ammunition and an array of other weapons donated by the US and its NATO allies in an operation many have compared to the Berlin airliftIn 1948 the Soviet Union blocked access to West Berlin by land and water. In response, the US and British air forces flew in supplies for its inhabitants, in an operation that lasted almost a year.. With the growing threat of Russia cutting off Ukraine's supply lines, it was a race against time.

The US has moved at extraordinary speed since President Biden approved $350m in military aid on 26 February. Within 48 hours the first shipments of arms were delivered to airfields near the Ukrainian border. In under a week more than 17,000 anti-tank missiles were in the hands of the defending army. Some have been used to attack and slow down a giant Russian convoy headed for Kyiv.

Washington has also been trying to broker a deal by which Poland supplies Ukraine with MIG-29A fighter aircraft designed in the Soviet Union. fighter jets from its air force and receives new F-16s from the US instead. 

The US has been helping in other ways too. Intelligence units based in Washington and Germany have intercepted messages from Russian forces and passed them on to the Ukrainian army. "Cybermission teams" from the US Cyber Command stationed in Eastern Europe are working to foil Russian digital attacks, helped by Microsoft.

And on Sunday secretary of state Anthony Blinken announced a move that could make all other economic sanctionsEconomic measures designed to punish a country, for instance by excluding it from trade. look insignificant. The US and its allies, he said, were in "very active discussions" about banning imports of Russian oil and natural gas.

These are not only vital to the Russian economy - they are a source of national pride. Novels and movies have been devoted to oil workers and engineers.

In recent years, there has been a tendency to dismiss the US as a spent force. The narrative goes that there has been a failure of leadership: Barack Obama did not stand up to Putin over Syria; Donald Trump was corrupt and incompetent; Joe Biden is too old to be effective.

And according to the political commentator Stephen M Walt, "The United States' foreign-policy elite has repeatedly shown an inability to recognise the limits of US power and set realistic objectives." Its dealings not only with Russia but with China, North Korea, Iraq and Afghanistan have all exposed those limits.

In addition, the country has been obsessed with and divided by domestic issues, such as race relations and gun control.

And yet, as Walt himself admits, "The United States is still the world's mightiest country." Although it has just 4.2% of the world's population, it contains 30% of the planet's wealth. It imports more than any other country and is the world's second-largest exporter. Its economy accounts for around 25% of the global GDPShort for Gross Domestic Product, the measure of all the goods and services produced inside a country.. 

Its armed forces, too, remain formidable. It is responsible for 39% of all military spending: $778bn per year, compared to China's $252bn and Russia's $61.7bn.

In addition, the US Department of Defence is the biggest employerIt employs approximately 2.9 million people. in the world, while Walmart is the biggest company.

Yes: No other country comes near it economically or militarily. It also has a huge cultural influence through film, TV and music. Its swift response in supporting Ukraine shows what it is capable of doing.

No: Its recent dealings with Russia and other hostile countries show that it is no longer the world-leading power it once was. If it had been, Russia would never have dared to invade Ukraine in the first place.

Or... It still has vast resources, but much depends on its leaders. Trump made terrible mistakes that reduced its standing in the world. It remains to be seen whether Biden can put them right.