Homeowners looking to protect their equity do everything they can to keep their neighborhood looking good and crime-free.

So, too, Americans looking to keep our nation free and prosperous should do everything they can to assure that our global “neighborhoods” remain stable and secure.

Our transatlantic neighborhood includes Central, as well as Western, Europe—from Ukraine, Moldova and Georgia westward. The three greatest threats to stability in this neighborhood are: the malign machinations of Russian President Vladimir Putin; spillover problems from the greater Middle East (e.g., waves of refugees); and the encroaching influence of China.

One way the U.S. can keep this neighborhood safe is to stiffen its future backbone: the line of states running from the Nordic nations through the Baltic states and the Balkans to Southern Europe. That arc delineates the front line in the standoff between Mr. Putin and the West. It is also an area with the potential to drive future economic growth for all of Europe.

But, although Central Europe’s democracies have joined NATO and the European Union, they remain hampered by the legacy of the Cold War. Most of Europe’s roads and rail lines run east-to-west and peter out in Central Europe. Economic evolution, long retarded by the U.S.S.R., still lags the West, and there are no major north-south economic corridors.

As my colleague at the Atlantic Council, Ian Brzezinski, wrote, “the region operates like a set of islands with limited connectivity and economic inefficiency.” That’s a problem that needs to be fixed.

These nations don’t need handouts, but they could use a hand up. In 2016, they launched the Three Seas Initiative to accelerate development of cross-border energy, transport, and digital infrastructure in the region. Austria, Bulgaria, Croatia, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania and Slovakia are pioneering the effort.

This is not a “big government” program. Primarily, they want to engage private sector interest and investment in this effort.

To that end, Poland, Romania and Estonia launched a Three Seas Initiative Investment Fund. Private sector managers will run the fund on purely commercial terms. Its goal: generate private investment in Three Seas region infrastructure projects and return a profit.

If this initiative is really going to get off the ground, however, all the nations need to kick in. They must develop a structured way for the private sector to engage. They must identify the projects envisioned and spell out the opportunities, risks, costs and potential rewards attached to each. And, of course, the countries will have to agree to work together.

If America wants a successful Europe—whole, peaceful and prosperous—Washington needs to gin up some momentum behind this initiative and do it now. This is likely the crucial year when the countries will decide whether Three Seas was just a pipe dream or serious project.

To be fair, U.S. officials have been verbally supportive. But to really energize this effort, Washington should put some skin in the game. It could support the Three Seas Initiative Investment Fund and use its existing capacities under the U.S. International Development Finance Corp., the Economic Support Fund, and Assistance for Europe, Eurasia and Central Asia to support projects in nations that contribute to the fund.

The U.S. could make its contribution contingent on all the Three Seas countries kicking in cash. If all the players ponied up, it would send a powerful signal to private sector investors that they should take the initiative seriously.

There is a precedent. In the 1990s, the U.S. created an Enterprise Fund for Central and Eastern Europe to stimulate private business investment in the region’s newly freed markets. The fund made money for its investors and helped jump start the region’s economic growth.

Once again, it’s the time for the U.S. to take a creative step to better its transatlantic neighborhood. It would make a big difference in Europe's future—and ours.