If you want to be real careful you should say Portland cement.

(because, for instance, the bitumen in asphalt roads is also a cement)

But you need cement to make concrete.

Yes, but if you're comparing usage across countries you probably want to compare the same thing; either concrete or cement.

Indeed but if you want a pretty good estimate you can just whatever mixing factor is most common in China or the US and convert :)

For anyone else that's curious, cement is mixed with water and some sort of aggregate to make concrete.

Don't forget the sand, which is technically an aggregate[1]. Using the wrong sand is a classic mistake being rediscovered in China:

http://www.wired.com/2013/03/poor-quality-chinese-concrete-c...

[1]-The concrete recipes I remember always had sand and rocks, gravel and/or pebbles (depending on local availability)

Yes, you want coarsely crushed ('sharp') sand, not sand that has better decorative qualities.