Is Adam the federal head of the human race?

Yes, Adam is the federal head of the human race. Scripture presents him as the first man, earthy, formed from dust, whose fall brought the need for restoration. Christ, the second Adam and Lord from heaven, is God's response to Adam's federal headship.

Les teaches that Adam is the federal head of the human race back in Genesis, and because Adam fell, Christ is the response to that federal headship. The first man, Adam, is of the earth and earthy, made from the elements of dust, while the second man is the Lord from heaven. The natural comes first, and afterward the spiritual. Les suggests, though he cannot prove it from Scripture, that Adam before he sinned had a body identical to Christ's in earthly appearance, being incorruptible and able to live forever had he not fallen. Christ, of course, did not fall.

Why is Christ the response to Adam as the federal head of the human race?

Adam stands as the federal head of the human race, and when he fell, restoration was required. Christ is the response to that fallen headship as the second Adam, the Lord from heaven. The natural came first, then the spiritual; the earthy Adam brought the need, and Christ is the one who restores.