Two giant, deafening, supersonic Soviet-era nuclear bombers are due back in Russia today after one of the most peculiar and troubling military missions of the post-Cold War era.

The pair of Tupolev Tu-160s have spent the past four days 6,000 miles from home on an air force base outside Caracas and over neutral waters in the Caribbean. They had three reasons for being there: to boost sales of Russian military hardware to Venezuela; as symbolic retaliation for the arrival of Nato warships in the Black Sea; and to cement a strategic alliance between two leading maverick, oil-rich autocracies, one from each hemisphere.

The first of these is at least rational from Russia's point of view. But the second is pointless, and the third betrays a profoundly reactionary agenda being pursued by both Moscow and Caracas at the expense of stability, progress and their own citizens.

The US State Department has rightly reacted with sardonic indifference to Russia's sudden interest in Venezuela. To news that the bombers would soon be followed by a battlegroup from the desperately rusty Russian Pacific fleet, a spokesman noted that at least “they found a few ships that can make it that far”.

To overreact would have been to fall into the simple trap of strengthening the Russian argument that Washington observes one set of rules for the former Soviet Union and another for its own backyard. As long as Nato ships are anchored off Poti and Batumi, and Nato advisers are working alongside the armed forces of Georgia and Ukraine, the US would be wise to maintain its relaxed attitude towards the nascent Chávez-Putin axis.

But this does not make it necessary, or beneficial to anyone. Claims of equivalence between Russian backing for Venezuela and Nato support for Georgia are as flawed and cynical as the view that invading South Ossetia was justified by the West's recognition of Kosovo's independence.

In Moscow and Caracas, authoritarian leaders are seeking to bolster the state and camouflage systemic corruption with populist rhetoric. Such regimes often need foreign scapegoats for domestic crises. Hence the expulsion last week of two US ambassadors, from Bolivia as well as Venezuela, both accused of fomenting coup attempts. No evidence was offered in either case, but the result is the appearance at least of a new left-wing challenge, with new great power backing, to US hegemony in Latin America.

Such a challenge will produce only losers. US dominance of the Americas is now overwhelmingly commercial and benign. The Monroe Doctrine is nearly 200 years old. Any Latin American country should be free to welcome Russian battlecruisers on pointless military exercises, but the last thing the people of Venezuela or Bolivia need is an ideological alliance against their most important trading partner.

Brazil and Argentina understand this. Their current leaders have won power through populism, but used it pragmatically. The results for free trade and international co-operation on crime, terrorism and drug trafficking have been remarkable. Persuading the people and political elites of Venezuela and Bolivia to follow suit will not be easy, but whoever next inhabits the White House must be ready to try.