One early beneficiary of the full-scale U.S.-Israeli attack on Iran has been President Vladimir V. Putin of Russia.

His government is profiting from higher oil and gas prices that could ease Russia’s economic woes. He is throwing around the country’s geopolitical weight as an alternative energy supplier. And he stands to gain on his own battlefield if the Middle East conflict strains the supply of U.S.-made air defenses for Ukraine.

But Mr. Putin is also grappling with the arrival of a new world of unbridled American power under President Trump, which is checking Russia’s global influence and ripping up Moscow’s playbook for partnerships abroad.

For years, Mr. Putin supported anti-American authoritarian governments in Iran, Venezuela and Cuba, with little worry that Washington would use its overwhelming military power to kill, capture or push out their leaders. That has now changed, as Mr. Trump has demonstrated a willingness to disregard international norms and engage in foreign adventurism by fully exploiting Washington’s might.

Even though Iran came to Russia’s aid with critical drones at the outset of Mr. Putin’s invasion of Ukraine four years ago, Russia has stood aside as the United States and Israel have pummeled Iran’s leadership and military. Moscow has issued little more than condemnatory statements that largely avoid naming Mr. Trump.

“It shows the limits of, ‘What does it mean to be a partner of Russia?’” said Angela Stent, a Russia expert and professor emerita at Georgetown University. She said the case of Iran was particularly stark given Tehran’s pivotal role in aiding Moscow in Ukraine.

The Kremlin spokesman, Dmitri S. Peskov, declined Friday to say how Moscow was helping Iran in its moment of need. A day earlier he said, “The war that’s going on isn’t our war.”

Washington’s actions against Russia-friendly leaders have come at a head-spinning pace.

The last two months have brought the U.S.-Israeli killing of Iran’s supreme leader, Ayatollah Ali Khamenei; the U.S. capture of President Nicolás Maduro of Venezuela; and a U.S. economic blockade intended to oust the Cuban president, Miguel Díaz-Canel. In every case, Russia has offered little visible help.

An American president pursuing foreign heads of state in their homes and offices, unchecked by Congress, has also flipped the script on Mr. Putin, who has made his appetite for risk, willingness to use force and unpredictability central to his coercive power in the world.

“Now he’s no longer the baddest guy in town,” said Bobo Lo, a Russia analyst and former Australian diplomat in Moscow.

“He no longer is able to strike fear in the way that he had hoped. That mantle has gone over to Trump,” Mr. Lo said. “And so Putin looks, in a way, a little bit pathetic.”