Obama said he looked "forward to continued close cooperation with Chancellor Merkel to address our common challenges in the years ahead," a White House statement said.
"The United States and Germany are close allies, and partner together around the world to promote freedom, security and prosperity," the statement read.
Britain's Prime Minister Gordon Brown said he wanted to extend "their close working relationship," according to a Downing Street spokeswoman.
French President Nicolas Sarkozy said the resounding win was a result of the public confidence Merkel had won in the past four years. Italian Prime Minister Silvio Berlusconi telephoned Merkel to underscore their "common vision and engagement to building a strong and united Europe," ANSA news agency reported.
Spanish Prime Minister Jose Luis Rodriguez Zapatero hit back at suggestions however that the right's victory in Germany was a new sign that the left-wing in Europe is in decline. "Is the wind favourable for conservatives? It is not true," Zapatero told Cadena Ser radio. "Each country votes according to its national circumstances."
Socialist leader Zapatero said that Germany's centre-left Social Democrats (SPD) had "suffered a correction". But he blamed this on the SPD for taking part in a coalition with Merkel over the past four years. "It is a situation in which, in the end you cannot define your own political identity and your project."
While the SPD suffered its worst post-war election result with only 23 percent of the vote, the 33.8-percent share won by Germany's conservatives on Sunday was their lowest in half a century. Turnout was also a record low of 70.8 percent against 77.7 percent four years ago.
Russia's Rossiiskaya Gazeta daily referred to the "record apathy" of voters and said the electoral campaign was "probably the most boring in the history of democratic Germany."
British newspaper, The Guardian, said: "Germans, in their present mood, are conservative social democrats, risk-averse, reasonably satisfied with what they've got, and bent above all on preserving it. Merkel answers that desire, embodying the intention to fight, quietly but firmly, domestically and internationally, to put Germany first." But it added that the poor score of the Christian Democrats leaves Merkel "vulnerable to back-stabbing within her party."
The Independent in Britain said the CDU's Bavarian allies, the CSU, had never taken Merkel to heart and could now become "restive."
The Dutch daily Trouw said the result was "historic", partly because of the right's low score. "Merkel will have problems giving the new government a social image," it commented. "The biggest problem will be the promised cut in taxes because it seems there is absolutely no money for that."
In Portugal, the Publico newspaper said there was a "bitter taste" in Merkel's win. "Merkel was saved by the historic score of the liberal Free Democrats and by the catastrophe which hit the Social Democrats."