It is the standard practice, worldwide, to stand for most of the Eucharistic prayer. That is the general rule, and a country needs a dispensation for additional kneeling. The general, worldwide rule is also for people to kneel during the consecration itself, then resume standing for the rest of Mass, not to stand during the consecration. The bishops of America sought and obtained permission to require kneeling not just at the consecration but through to the Great Amen, and that is the rule here. (source: Catholic Answers)
As explained in the General Instruction of the Roman Missal, number 43:
In the Dioceses of the United States of America, they should kneel beginning after the singing or recitation of the Sanctus (Holy, Holy, Holy) until after the Amen of the Eucharistic Prayer, except when prevented on occasion by ill health, or for reasons of lack of space, of the large number of people present, or for another reasonable cause. However, those who do not kneel ought to make a profound bow when the Priest genuflects after the Consecration.
Making a profound bow “when the Priest genuflects after the Consecration,” certainly suggests that if we are not kneeling, we should be standing. Of course, the concrete floor in our hall is a good reason for many of us to stand rather than kneel for the length of the Eucharistic prayer, however, those who are seated should be limited to those who cannot kneel or stand due to age, health, or other reasonable cause.
Read more in the “Why Do We Do That?” series from Deacon Mike Fritz.