Without the FEMA provision, Puerto Rico could have to pick up 10 percent of the rebuilding costs — billions of dollars the commonwealth government, whose finances have been controlled by a federal oversight board since 2016, said it does not have.

That is why Gov. Ricardo A. Rosselló, other Puerto Rican officials and their allies on Capitol Hill have cast the disaster relief package as critical for the island’s long-term rebuilding. The legislation would not provide direct funding for projects like the Vieques hospital, but it would help ensure that the Puerto Rican government’s budget troubles don’t hold the project up.

“This affects everything,” Mr. Rosselló, a Democrat, said in an interview last week. “It hinders the recovery. It hinders our objective of having an energy grid that is sustainable, that’s reliable and that’s modern. It hinders our capability of fixing our water systems.”

Also awaiting funding: police stations, public schools and roads. The town of Villalba needs to replace its emergency operations center and an assisted living facility for seniors, both destroyed by the hurricane, Mayor Luis Javier Hernández said. (The town has leased other buildings to house the facilities in the meantime.) Residents of nearby Barranquitas, in Puerto Rico’s mountainous central region, have had to take 40-minute detours along country roads because two major bridges were washed out.

“It’s been dangerous, and there have been several accidents,” Mayor Francisco López of Barranquitas said. “It’s really concerning, because the hurricane was a year and a half ago — and we’re two months from the start of a new hurricane season.”

In the San Juan neighborhood of Ocean Park, where some streets were flooded with smelly water for two weeks after Hurricane Maria, Jesús Herbón, the owner of a local bakery, jokes that he has become an expert on water pumps from all the time he has devoted to learning about how they failed during the storm.