Tell me again how putting billions of dollars into infrastructure and roads is going to help the (for example) 5K? people laid off from Microsoft?
Do you suppose they know how to operate heavy machinery? Are they all going to pick up a shovel? I just don't get it, I guess.
A bridge being built means workers getting jobs. From the people designing it to the people building it. Add to that, the secretaries and the janitors in the office to the people making the steel and the concrete to the truckers hauling the materials now have work; not to leave out the food vendor with his "roach coach".
All these people now working on this bridge and it's various components and support positions now have money to spend on things like food, cars and yes, computers (which puts Microsoft to work). And the people that makes the cars now have money to by computers. Business that get the contracts to build the bridge and its components now have money to up-grade their computers putting Microsoft to work.
Multiply this by a couple of hundred bridges and a few thousand miles of road across the country and the effects are multiplied exponentially.
The point is putting people to work in one sector of the economy has far reaching effects in all areas of the economy.