I strongly disagree. USAMO problems range in difficulty quite a bit. I can solve some but certainly not all. Not so for IMO. And nowadays I generally solve all of the Putnam problems in the time allotted.
By the way, the early years of the IMO were very easy, by today's standards (only a few countries were involved at that point). They would probably be approachable to people comfortable with the AIME problems.
By the way, the early years of the IMO were very easy, by today's standards (only a few countries were involved at that point). They would probably be approachable to people comfortable with the AIME problems.