President Donald Trump's election in the United States and the vote by Euro-skeptics in the United Kingdom to leave the European Union were both fueled by a populist turn in politics, a nostalgic desire to bring the center of economic and political power "back home." The implications for cities in both countries were entirely different.

The role of America's city leaders in solving some of the nation's most pressing problems has been elevated, but that has occurred in reaction to Trump's abdication of national responsibility for the challenges of climate change and inequality. The Brexiteers, on the other hand, further empowered national policymakers at the expense of local leaders who are closer to the problems they need solved. Neither outcome is positive. The world needs empowered cities and strong city-to-city networks pulling in the same direction as the nations whose economies they fuel.

But cities and their mayors cannot afford to wait for party divides and angry populism to subside at the national level. They are taking responsibility for the prime challenges of modern societies: demographic transformation, economic insecurity, cultural anxiety and climate change. This new wave of urban problem-solving, or "New Localism," showcases how cities are networks of public, private and civic institutions that co-produce the economy and co-govern critical aspects of urban life.

Successful mayors help people and organizations collaborate to solve problems and do together what they cannot do alone. As a new Brookings Institution paper finds, mayors who embrace this networked leadership are making a material difference in the cities they lead. Louisville, Ky., for example, launched a Cradle to Career initiative aiming to give children and young adults the help they need at every stage of the life cycle. Pittsburgh's tight network of civic institutions, anchor universities and corporations has enabled the transformation of the city's economy from one dependent on heavy industry. Inside the City Hall of Bristol, a city of more than 454,000 in southwest England, the radically reconfigured "Cash Hall" is an open, collaborative space for city staffers and civic, private and university partners.

While these examples show how mayors can lead in any political context, their formal powers can also make change at scale. In the U.K., most cities lack the powers to tax, spend and plan that many U.S. cities take for granted; local authorities in the U.K. spend only 7 percent of the tax revenue collected in their areas. By contrast, the mayor of New York oversees spending decisions for a large portion of revenues collected from local income, sales and property taxes -- funds that can be deployed to leverage private investment for education, housing and infrastructure. Devolving more formal powers to local governments will enable a diverse array of solutions to pressing local challenges.

Though the devolution agenda has made strides in the U.K. and new "metro mayors" gained new powers in six metropolitan areas in May 2017, government in the U.K. remains one of the most centralized in the world, and its cities suffer from it. There is a danger that the national government will be too distracted by the Brexit negotiations to focus on the domestic devolution agenda. Instead, it should accelerate devolution initiatives, starting with giving local governments control over business tax rates, a commitment the government promised to deliver on by 2020. This would give cities greater power to raise revenues and invest in critical local services and priorities.

The need for more empowered cities is not limited to the U.K. or the U.S. Strong local-government leaders around the globe need the ability to influence what happens not only within their boundaries but also in the national, international and global arenas where strategic priorities are set. The Global Parliament of Mayors is an example of an action-oriented city-empowerment network that aims to establish mayors as legitimate and appropriate leaders to respond to global issues.

New Localism is shattering notions of where power lies, who wields it and how transformative change occurs. It is upending conventional wisdom about who solves problems in an age of partisan conflict and deep divisions over common purpose. We need disruptive institutions in these disruptive times: bodies focused on making real governance shifts that empower cities in a world already powered by them.