We have travel insurance through our bank, but it didn't kick in until we had been resident in the UK for 6 months. One of our credit cards provides very comprehensive insurance for trip cancellation, lost baggage etc. so you might want to check your coverages to see what is provided.
But if you're talking about emergency medical coverage in the USA you'll probably have to check with the individual insurers offering annual policies as they don't all have the same conditions, or take out single trip insurance.