The "ticking time bomb" notion may be a bit overdramatic. A radiologist reads the scan immediately, and if he did not think it was safe for you to wait three weeks to be seen, he would have alerted you that it was urgent. If you want to compare the aneurysm to a time bomb, it's one with a long, long, timer. I don't know whether the aneurysm is going to need to be operated on or not, but I think you can relax about the three week wait. When you do have your consultation, you can ask the doctor how long the aneurysm has probably been in the process of forming, and that will give you some perspective. It may have been there for years.
If it turns out the aneurysm does need to be operated on, I would want my surgeon to be someone who repairs splenic aneurysms on a regular basis, and that's not going to be just any surgeon. I have had a thoracic aortic aneurysm, and so I know how you feel when you hear the word aneurysm, but it is more important to take the right steps than to take fast steps. Whatever decisions you make need to be the right decisions, so even if you end up needing a second or third opinion, that's okay. I would want to have a consultation with a surgeon who is an expert in splenic aneurysms. If you want to put your anxiety to good use, you can start asking around for the names of the best surgeons in NYC for splenic aneurysms. I would not feel satisfied until I had a consultation with one of those particular surgical experts. Good luck.