There are 18 tracks in the game. You don't need to win, just finish the race so put it on easy and 15% race length to save time.
If you're playing through career mode, Laguna Seca won't be raced until MotoGP class. It isn't raced in Moto3 or Moto2 but you can do it in Grand Prix mode in MotoGP class.
The tracks in order of career mode are as follows:
1) Losail (Qatar)
2) Austin (Texas, Circuit of the Americas)
3) Jerez (Spain)
4) Le Mans (France)
5) Mugello (Italy)
6) Catalunya (Spain)
7) Assen (Holland)
8) Sachsenring (Germany)
9) Laguna Seca (USA - only available in MotoGP class)
10) Indianapolis (USA)
11) Brno (Czech Republic)
12) Silverstone (UK)
13) Misano (Italy)
14) Aragon (Spain)
15) Sepang (Malaysia)
16) Phillip Island (Australia)
17) Motegi (Japan)
18) Valencia (Spain)