We are Canadian based. When we left Vancouver BC, headed south, we got a worldwide policy (International Travellers series, I think) from MultiNational Underwriters. To keep the cost reasonable, it has a $5K deductible. We think of it as "heart attack" insurance.
It restricts us to spending not more than 6 months per year in the US.
In Mexico and elsewhere, medical costs are much lower than US costs. But a cruiser who had a heart attach in Mazatlan MX, and was airlifted to Guadalajara (and got excellent care, with bypass operation) was out-of-pocket about $25K.