In order to be licensed in most (all?) states one has to be a graduate of a medical school listed in the World Health Organization (WHO) World Directory of Medical Schools. This is a UN publication. WHO sends a questionaire to the appropriate officials in each country asking them to list the medical schools recognized by whatever authorities in the country are responsible for "accrediting."
This listing is not necessarily a seal of approval of quality, just official recognition. The WI medical schools get approval from the local governments, not the US. Many give approval because the graduates will not practice in that country and it is a source of revenue, especially US dollars. This comment is in no way meant to impugn the quality of the medical education, which is quite high in some of them, but recognition is not necessarily a judgement of quality. It IS in the US and major countries in the world.
In the US, accreditation is the responsibity of the Liaison Committee on Medical Education (LCME), a joint committee of the AMA and AAMC. In most countries, it is the government that decides.
An on-line medical school, not recognized in the country in which it is based, will not allow anyone with a degree from them to become a licensed physician, or even to get a residency, also required for licensure, in the US.
Whether or not US medical schools have some on-line learning services is irrelevant.
Whether on-line learning is efficent and sufficent is also irrelevant. A graduate of a foreign medical school who wants to practice in the US must be eligible to sit for a four-part national examination, 3 parts of which are the same that US medical school students take during their passage through medical school and residency; FMGs now have to take a fourth part, a practical exam in medical skills. More than half of medical education is practical experience with patients. Residency training is all working with patients and a US residency is impossible without a medical degree from a WHO listed medical school.
Caveat emptor, Latin for let the buyer beware.
Anyone who wants a medical education should not waste time and energy arguing the merits of on-line medical education. It will not get them what they must have to get a medical education and licensure.