Should We Kneel at Mass?

The General Instruction of the Roman Missal instructs:

In the dioceses of the United States of America, [the faithful] should kneel beginning after the singing or recitation of the Sanctus until after the Amen of the Eucharistic Prayer. (GIRM 43)

This applies even if there are no kneelers, unless conditions such as lack of space or physical infirmity apply.