The attitude among those responsible seems to have been "well, that bridge has been fine for 60 years, it can last another 10 until we get around to it." On the averages that attitude may actually be acceptably responsible. Disasters like the recent bridge collapse are actually extraordinarily rare despite all of the shortcomings of our infrastructure maintenance. Plus there are funding and manpower limitations to take into consideration, as well as the problems caused by closing roads and bridges in busy areas. However, none of these reasonable excuses makes things any better for the families of those killed or injured, and they don't mean we can't do a lot better.
Federal and state spending on highways, bridge and tunnel maintenance comes to over $30 billion a year, but that's clearly not enough to solve every problem immediately. At that rate of spending, if we have $1.6 trillion worth of work to do we won't have all the problems fixed for 50 years, long enough for another couple of trillion worth of new problems to develop. Nonetheless, some progress has been made. Although an alarming 13% of bridges nationwide have been rated as structurally deficient. That's actually a 10% decrease since 1990, so some slow progress is being made.
Some are already trying to attach blame for the state of our infrastructure on the Bush administration and in particular on the big cost of the conflict in Iraq. But the truth is that federal funding for infrastructure maintenance has increased substantially every year, even when other budget items have been cut. What's more, much of that spending is through the Department of Transportation which plans spending on a 6-year cycle, so their level of spending was planned out well before the Iraq invasion. That spending level may have been set too low, but the Clinton administration did make a pledge in 1998 to try to speed up infrastructure maintenance with corresponding higher appropriations, which have continued during the Bush administration.
If we have to focus on a guilty party it might be more appropriate to look at the various state governments, because about 75% of the funding and responsibility for highways, tunnels and bridges rests with them. It is also on the state level where money is most easily diverted, including federal money which is allocated largely on the requests of state governments, so if their priorities are screwed up or politicized then everyone's money gets misspent.
On the positive side, this is a solvable problem. Just increasing federal spending by $10 billion a year with a proportional increase in state spending on infrastructure maintenance would eliminate any major problems within 20 years - not unreasonable for a problem which has been building up for a hundred - with the most critical situations solved within the first couple of years. There are, of course, secondary aspects to consider. For example, we can't very well afford the labor shortage which extremist immigration measures would cause and still meet the demand for additional labor which such a large expansion in construction would create.