WASHINGTON—The U.S. government’s budget deficit surged to an all-time high of $1.7 trillion for the first six months of this budget year, nearly double the previous record, as another round of economic-support checks added billions of dollars to spending last month. In its monthly budget report, the Treasury Department said Monday that the deficit for the first half of the budget year—from October through March—was up from a shortfall of $743.5 billion for the same period a year ago. The deficit has been driven higher by trillions of dollars in support Congress has passed in successive economic rescue packages since the pandemic struck in early March 2020. The latest round came in a $1.9 trillion measure that President Joe Biden pushed through Congress last month. Biden’s package included individual support payments of up to $1,400 and the administration rushed to make those payments as soon Biden signed the measure into …