The Trump administration has unexpectedly halted a project to protect the New York City region from flooding during dangerous storms like Hurricane Sandy — a decision that came six weeks after President Trump took to Twitter to ridicule the study ’s most expensive proposal, a giant sea wall that could have cost billions of dollars. The Army Corps of Engineers’ announcement that the project was “indefinitely postponed” surprised some of its own officials, and local politicians and advocates said the decision was stunning at a time when climate change is threatening New York’s future with intensifying storms. In a statement, the Corps’ New York office said only that the study was suspended because it did not receive funding in the agency’s work plan for 2020. Officials there refused to comment on whether they believed that Mr. Trump had influenced the decision. […]