Standing at the barren former industrial site at Assembly Square, Somerville Mayor Joseph A. Curtatone last week derided Congress - and Senator Scott Brown - for holding up President Barack Obama’s jobs legislation. Although the legislation has no direct impact on the Assembly Square project, in the works for nearly a decade, Curtatone used as an example the $25 million the city will spend on infrastructure improvements to spur the development. “What we’re doing in Assembly Square is what we should be doing across the country,’’ Curtatone said. “This is the kind of thing we send representatives to Washington to do.’’ Planners expect the massive mixed-use development to create 10,000 short-term jobs and and an additional 10,000 permanent positions. If anything, the press conference was a savvy mating of a national issue with a local project that, unlike others in the region of its scope and caliber, managed to survive the 2007-2008 crash of the credit markets. In addition to the state Democratic Party, which helped stage the briefing, local and national groups have echoed the call for Brown to vote to pass the jobs bill. Curtatone said the briefing was an outgrowth of a meeting with state Democratic party leaders during a recent visit to Washington.