In general and in the workplace, Americans are known for speaking up and generally going after what they want. Particularly in the workplace, you may be surprised to see that Americans are not afraid to voice their ideas. While your supervisor is your superior and should always be treated with respect, it’s okay not to hold back and ask a question if you have one.
If you need clarification on a project, your employer would prefer that you let them know. While there is certainly a difference between speaking up and being subversive or rude, it’s okay to say something!