Just to be clear, BCA's insurance is not travel insurance. It won't cover you for rescue, for injury to yourself of for medical care and repatriation. Snowcard is realistically the only place to get that cover, although you may want to check out Dogtag too as that is who we used for Mulu this year as it is cheaper than Snowcard.
There is very little choice in the market place for overseas caver insurance cover. Some of the other players (Post Office, etc.) offer the same (or substantially the same) policy as Snowcard at a fairly similar price. Their policies are basically underwritten by the same insurer and the cover is very similar.
Snowcard have a track record of paying out and the Assistance International (I know you said USA) organisation they use to manage emergencies have shown to be both reliable and consistent. On a rescue I was unfortunate to be closely connected to a couple of years back, Snowcard and Assistance International sorted everything for the people concerned, including a full cave rescue, helicopter evacuation and hospitalisation, followed by homeward travel. Seamlessly, painlessly (except for the victim with the broken pelvis...) and efficiently. I know who I will insure with if I am caving in Europe.
As for world wide, Dogtag are substantially cheaper than Snowcard, seem to offer a suitable policy, BUT there is no track record of a claim that I know of. That doesn't mean that they are crap, as I said I used them for Mulu, but for a personal recommendation of service you need to experience the service. Luckily nobody needed rescuing in Mulu this year, not even Colin Boothroyd...