It was never 'illegal' to have a home birth 'in the USA' under federal law. Laws governing home births are made by individual states, not the federal govt.
Different states did and do have different requirements for who can attend a birth.
Nebraska's is the strictest; only an MD can attend a home birth. The rest of the states laws vary as to who can attend a home birth, but they all require some kind of licensure or certification.
In my state (CA) you must be either a certified nurse midwife or a licensed midwife.