Limited:
We have found that our US health insurance and credit card coverage is very limited for international trips AND does not offer the emergency evacuation that is important to us.

The cost of a dedicated travel insurance plan (usually 5-10% of your non refundable trip costs) is well worth the financial hardship that could occur due to the unexpected international--medical or otherwise (London subway attack this week). We have used GENERALI Travel Insurance (used to be CSA) that will work with your US health plan as primary/secondary to work out coverages and who pays what. We did not have to get involved. GENERALI handled the process directly including obtaining documents from Royal Caribbean for our claim. See their website for advice on trip with multiple travel suppliers: https://www.generalitravelinsurance.com/faqs