Open Question: Does every employee in US gets a medical and pension/ retired pay coverage by the employer?

Does every employee in US gets a medical and pension/ retired pay coverage by the employer? Is it employer's obligation/ liability to ensure an employee, and is the employer obliged by the government to do so? And if yes, where do they store the coverage- in some statistics by one's Social Security Card number??? And also does the pension plan works the same for foreigners? Thank you in