Did San Francisco sink into the bay? It looks like the map didn't include it, shame since that's probably the only place outside NYC that may be a different color.
EDIT:
Looks like someone else noticed it to and did a close up on the original. It shows SF is public transit and also shows that dc is missing on this map as well and also is more public transit then driving, so not just New York. You can also see it by borough in NY and Staten Island is cars but Hudson county NJ is public transit too.
The choice of measurement is a misleading one. We do have a handful of cities with good transit options but this choice of measurement shows them all as green. Many developed countries will show most/all green, not just the US, as if they have the same car culture.
Depends what you mean by in SF. That is a study of the entire bay area asking how they get to / around SF. That makes sense, most people in the bay area coming into the city are suburbanites who drive in. You'd probably see the same for NYC as well, barring Manhattan which is more or less hostile to driving. People who live in the city though primarily get around by walking transit. The same study says :
San Francisco residents still used priority modes twice as often as non-residents for trips within San Francisco.
So it's the dominant mode for people traveling in / through SF but not for people who live in SF.
In my original comment I put an edit in with a link to the original and SF is orange, along with DC which you can't see on this either.