Does chip and Medicaid cover absolutely everyone who might need it? Are there people who, despite the coverage, are still left with outstanding costs they can't

Does chip and Medicaid cover absolutely everyone who might need it? Are there people who, despite the coverage, are still left with outstanding costs they can't meet? My understanding is that in Cuba, there is no applying to services like Chip, or Medicaid. Theres no chance you won't get coverage, as everyone, by default, gets the care they need. Wait times are non existent for the pregnant or disabled across the country, not just in certain regions. It doesn't seem totally unlikely that the people that """"fall through the cracks"""" in the American systems are enough to swing infant mortality rates.