His analogy misses a lot of subtleties.

Consider cars.

He says something like "we fixed the problems with cars". I say "what problems and what we"? Technologies change the social and political order, sometimes preventing us from solving their problems.

In the U.S., cars changed the landscape in a very different way from the rest of the world. Because the car industry got a lot of political clout they were able to restrict public transportation (particularly in cities) and built an environment where you're barely functional without a car if you live outside New York or San Francisco (both cities had public transportation before the car industry came up). The rest of the world uses a lot more buses, trains and bicycles than the U.S. does.

Cars created a world with methyl-lead gasoline, global warming, corrupt petro-cleptocracies and several other distortions that we didn't completely fix yet. Mr. Gates only talks about accidents and drunken-drivers. That was easy because the responsible for those problems don't have political and economic clout. Now good luck trying to fix the problems caused by people with lots of money (e.g polluters, big tobacco, health insurance industry) or lots of votes (e.g. cars and guns owners).