看一下官方原文
The top-scoring AMC 10 participants (based on a combination of AMC 10 and AIME score) are invited to take the USAJMO. U.S. citizens and students studying in the United States and Canada (with qualifying scores) are eligible to take the USAMO and USAJMO
Students who perform exceptionally well on the AMC 10/12 are invited to continue participating in the AMC series of examinations that culminate with the International Mathematical Olympiad (IMO).
The first in this series is the American Invitational Mathematics Exam (AIME), followed by the USA Mathematical Olympiad and Junior Mathematical Olympiad (USAMO and USAJMO).
The top USA(J)MO participants are invited to the Mathematical Olympiad Program (MOP) in the summer after the competition.
Participants from the Mathematical Olympiad Program are then eligible to be selected for the following summer’s six-member team that will represent the United States of America at the IMO.