Hi Chick,
I would thoroughly recommend taking some medical insurance to the US. I have built hours there for many years and whilst everything is fine, the peace of mind is worth it. Flying is not "Dangerous Sports" but the standard medical insurance have exclusions if you are "Flying as aircrew". You need the standard medical insurance with a policy extension to cover flying as aircrew. I normally use Pentagon Insurance in either Jersey or Guernesy - I forget which. They normally offer cover with a company called Holmans, and world wide for the year, including flying risks is about £90.00 - money well spent. Check the web or the back pages of Pilot magazine.
Enjoy the flying
Tailwinds