score:7
Strictly speaking, you can only carry in medication that is for your own personal use -- otherwise, you are importing the medicine and this would cause all sorts of problems.
While in reality, if it's not a controlled or scheduled substance and the quantity that you are taking in would be reasonable for personal use, the custom's agent won't normally flag it but if caught you would be technically in violation and it would be within his rights to confiscate the medicine, fine you, or bar you from entry into the USA:
Note: relying on the internet for advice for behavior that can get you deported is dangerous. We could tell you that it was ok, that you wouldn't get caught, that customs has bigger fish to fry, but you're the one whose status would be in jeopardy.
Keeping it cold: Note that the airplane will not let you use their onboard cold storage units for liability reasons (you could contaminate the food or vice versa). You should use a small cooler box with ice or ice-packs (blue-gel, etc.) to keep the insulin cold. You can ask the flight staff for more ice during the flight, which they may or may not give you.