Ten years ago, a general pessimism began to set in among some pundits and technologists who convinced themselves that America can’t do big things anymore. But they only got it half right.

Although the U.S. had created digital services like Facebook, these thinkers noted, massive technological efforts to match the scale of the Manhattan Project to develop nuclear weapons, the Apollo moon landings, or big infrastructure projects like the Hoover Dam or the interstate highway system, seemed out of reach in the modern era. Countries like China boasted massive dams and ultra-fast trains, while the U.S. could barely repair its roads or keep Amtrak running.

This concern was shared by figures as diverse as Silicon Valley billionaire Peter Thiel and President Barack Obama. When the COVID-19 pandemic hit and the U.S.seemed unable to carry out mass testing or even produce enough masks for hospital workers, the perception of American ineffectuality was reinforced.

But then, this month, that changed. Researchers at Moderna Inc. and Pfizer Inc. both announced preliminary results showing that their COVID-19 vaccines are more than 90% effective against the pandemic virus. The first shots could start going into Americans’ arms within weeks.

This is a monumental feat. Typically, developing a vaccine takes 10 to 15 years, and the fastest ever recorded previously was four years (not counting variations on existing vaccines such as flu shots). This time, multiple vaccines were created in less than a year. And unlike China, which also developed vaccines very quickly, American researchers used a whole new type of vaccine, which will be hugely useful against future pandemics.

This was not solely a U.S. accomplishment; Pfizer partnered with the German company BioNTech SE, and funding came from the German government. But the development was possible in part because the U.S. Biomedical Advanced Research and Development Authority committed up front to buying a large amount of the vaccine if it was successful. And Moderna’s success was the result of an all-American public-private partnership, with the National Institute of Allergy and Infectious Diseases and BARDA both pitching in large amounts of resources.

The COVID-19 vaccination effort isn’t the only big thing the U.S. has accomplished in recent years. Solar power, which not so long ago was so expensive that it was treated as a mere environmentalist pipe dream, has come down in price by a factor of 300 since the late 1970s. In just the last decade, solar costs have declined by over 80%, while battery storage has fallen even faster in price:

While some of the solar-cost decline has been due to China producing panels on a massive scale, much of it was due to research funded by the U.S. government. The same is true of advances in lithium-ion batteries, where one American company in particular — Tesla Inc. — has been instrumental in pushing down costs. Together, solar and batteries promise to spark a true energy revolution, which will not just help save the world from climate change, but will bring back the days when society could expect cheaper energy every year. And much of this revolution was due, once again, to U.S. public-private partnerships and decades of far-sighted effort.

COVID-19 vaccines and cheap, clean energy are the modern-day Manhattan and Apollo projects. They prove the U.S. can still do big things when it wants to — at least, in science and technology.

But there is one important area in which Americans have lost their ability to get big things done. Thanks to out-of-control construction costs, the nation has been unable to build the type of monumental infrastructure projects that powered growth in past eras. Many of the important undertakings facing the government — building a modernized energy grid, creating denser housing and public transit in the suburbs, retrofitting buildings to use electricity instead of gas, and cleaning up lead pollution — will founder if the government can’t find some way to bring down costs, while ideas like high-speed rail will remain pipe dreams.

Why can the U.S. do big science but not big infrastructure? It’s mostly a matter of political will. The U.S. allows construction projects to be held up by a near-infinite series of regulatory and legal challenges, causing costly delays. Governments use dysfunctional processes that award contracts to firms that are expensive, overstaffed and slow. And states generally fail to override the prerogatives of local governments, which are often dominated by politically powerful homeowners who try to prevent anything from being built near their houses.

So the U.S. needs to apply the same urgency and political will to construction that it applied to vaccine development. Costly delays and interruptions need to be bypassed or forbidden, inefficient contracting processes must be reformed, and state politicians have to override local ones. Instead of treating construction as a luxury, a jobs program or an opportunity for pork-barrel spending, the government has to make it a priority.

America still does big things in the scientific realm, but to meet the challenges of the 21st century, it has to be better at building things in the physical world.

(Noah Smith is a Bloomberg Opinion columnist. He was an assistant professor of finance at Stony Brook University, and he blogs at Noahpinion.)