From SIGHT Magazine:
In the United States, Catholics kneel during the Eucharistic prayer while Catholics in the rest of the world stand. Many European churches, especially the older ones, do not even have kneelers.
After the Second Vatican Council, the General Instruction of the Roman Missal (GIRM #43) mandated standing during the Eucharistic prayer, but the US bishops asked for an exception. In the United States, we kneel “except when prevented on occasion by reasons of health, lack of space, the large number of people present, or some other good reason.” The bishops believed that American Catholics would be scandalised if they were asked to stand during the Eucharistic prayer. The Vatican granted the US an exception to the universal rule.