Is there a large difference to colleges between making USAMO (score of 221) and a 219.5?
I mean, one is USAMO and the other isn’t.
Lots of information is gathered and review and probably precious few are tops in every category. However, admission decisions are designed to assemble a class. Applicants are not rank ordered meaning applicants with somewhat lower wonderful profiles may be admitted. If a school admits very few applicants, then a slight problem may get you denied. But when profiles with minimal differences are reviewed by admissions at less intense schools, a small glitch may be lost when included in an otherwise excellent profile and an applicant is admitted.
Reality. Very little guarantees admission. If you agitate about the impact of a wee portion on an application, you can make yourself nuts with worry and the thing that most bothers you may have been irrelevant in the actual decision. You will never know. Don’t sweat the small stuff!!!
I missed USAJMO in 10th grade by 1.5 points. As @thinkingfastslow said, I think it makes a big difference. If I had just left one more question blank on the AMC 10, I would probably feel much more comfortable about college admissions now. There’s no real way to say, “I missed USA(J)MO by 1.5 points!” on your application without sounding like a tool, unfortunately.
It makes difference. But there is nothing you can do about it. Forget it and move on.