It was never meant to be as a western.
OUATITW was Leone's swan song to the western and the beginning of a new trilogy, North America:
OUATITW marks the end of the west as the last scene clearly shows: the pioneers, the gun fighters
and outlaws are leaving the scene, the railroad brings the east to the west which in Jill finally found
a 'mama'. Always important for a civilized world

.
GIU LA TESTA shows the results of industrialization and landgrabbing: poverty among the lower classes,
fat rich men who gained control under the capitalism. Revolution is the answer.
OUATIA finally is dedicated to the last period of American outlaws, the depression with its hoods, Prohibition
and the beginning of massive corruption in police force and politics - by then the criminal weight finally shifted
from the obvious outlaw bad guy to politicans (which brings us to nowadays

).
France is the only country, were all three titles indicate this clearly for the audience:
IL ETAIS UNE FOIS DANS L'OUEST
IL ETAIS UNE FOIS LA REVOLUTION
IL ETAIS UNE FOIS EN AMERIQUE
Most misleading the titles were in my native Germany. ONCE UPON A TIME is the beginning of all
the fairy tales (Brothers Grimm etc.) which was supposed to be not working for western (the distributor thought).
So most of the Italian westerns, and action films in general, had to have strong violent action-oriented titles
like ENEMIES OF DEATH (Five Card Stud), KILL, AMIGO! (Quien Sabe?) or BODIES ARE COVERING HIS WAY (Il grande Silenzio). OUATITW became PLAY ME THE SONG OF DEATH (they even dubbed in that line, when Bronson gives
Fonda the harmonica before the dies). GIU LA TESTA became MELODY OF DEATH (Todesmelodie).
I love all three. Before them the DOLLAR - trilogy was groundbreaking, hip & cool and adorable. For almost 30 years I'm watching them now and never get tired of them.
But the 2nd trilogy in its whole is not as easy to love because sitting back and enjoy is not enough here. Thank god,
it shows how Leone developed over the years. A rich body of work.