At a time when some had begun to question how long America's pre-eminence in science and diplomacy could last, nine of the 11 nominees who won or shared this year's five prizes handed out so far are American.
On Monday, the economics prize will be announced, and Americans are the favorites.
The scientists were recognized for work that led to breakthroughs in cancer therapies and antibiotics, and brought the world digital photography and high-speed Internet. Obama won for his mission to rid the world of nuclear arms and to bridge the divide with the Muslim world.
He is the third sitting president, after Theodore Roosevelt and Woodrow Wilson, to win the prize. Jimmy Carter got it after he left office, as did former Vice President Al Gore. No country comes closer to boasting so many leaders with Nobel laurels.
Obama's triumph capped a giddy week for Nobel-watchers in which the big U.S. disappointment was in literature. After great expectations for Philip Roth or Joyce Carol Oates, the prize went to Herta Mueller, a Romanian-born German author.
The chief of the Royal Swedish Academy of Sciences sees two big reasons for the U.S. dominance in science: money and ambition.
Gunnar Oquist, permanent secretary of the group that picks the chemistry and physics winners, cited a U.S. willingness to pour money into research and an eye for the big breakthrough, as opposed to incremental steps forward.
"In Europe, they are focusing on high production with good enough quality," he told The Associated Press Wednesday.
However, Alan Leshner, chief executive officer of the American Association for the Advancement of Science, noted that Nobels are generally given for work that's a decade old or more, and that the U.S. mustn't become complacent.
U.S. strength reflects federal financial support since World War II, but it has flattened out or declined while other countries are investing heavily in their own scientific research, he said.
"The United States probably will not lose its eminence in science in the coming years, but its pre-eminence, its dominance is, of course, at risk as other countries make their own investments," he said.
While Americans lag in categories such as literature, they hold more than 40 percent of the physics, chemistry and medicine awards.
Jeremy Berg, director of the National Institute of General Medical Sciences in Bethesda, Maryland, said ample federal money gives American scientists confidence they can tackle daunting, long-term problems without feeling pressured to produce fast results or lose funding. Obama has said he wants to boost investment in science.
Gunnar Karlstrom, a chemistry professor at Lund University in Sweden, said high salaries for researchers make the U.S. attractive to foreign scientists.
Ulf Lagerkvist, professor of medical biochemistry at the University of Gothenburg, insisted that even though the prizes may have been awarded to many U.S. citizens, the award is in fact "to a very high degree international."
"The Americans have proven very good at recruiting from around the whole world," he said, noting that they offer both better research opportunities and funding.
"It's incredibly much easier to get money from the American Congress than it is from equivalent institutions in Europe," he said.
Europe and Asia have their share of Nobel Prizes, but of the 816 winners since the first awards were made in 1901, 309 have been American. The next closest is Britain, with some 114 winners.
The Nobel Foundation keeps no official tally of citizenships since laureates often have more than one.
Berg, the American, noted that other countries have begun to build up their own scientific establishments, and could well enlrge their share of prizes.
"It's the science that's important, and the fact that there are more countries investing in it, I think, is a great thing," Berg said.
The European Union's executive body has weighed in on the debate. A new EU-commissioned report says Europe lags well behind Japan and the U.S. in funding for research and development as well as higher education. It suggests targets for 2030 of more than doubling research and development funding to 5 percent of gross domestic product, and tripling spending on higher education to 3.3 percent of GDP.
It says EU countries too often prefer funding projects within their borders instead of contributing to others with bigger potential.
"Lots of small initiatives" are no solution, said Professor John Wood, head of the European group that wrote the report. "We cannot have 27 member states playing small games everywhere."
AP Science Writer Malcolm Ritter in New York and AP Writer Raf Casert in Brussels contributed to this report.