In Germany, I can buy travel health insurance that covers an unlimited number of trips abroad of up to 8 weeks each (including basically any doctors and hospitals abroad, as well as transport back home when medically recommended) for about 15 USD a year, and similar insurance for trips up to 1 year for about 500 USD a year. (Valid worldwide, or excluding North America for a cheaper rate.)

(Recommendations (in German): https://www.finanztip.de/krankenversicherung/auslandsreisekr... )