Tridentine Mass was essentially unchanged for 1000+ years.
You would not have been able to find any other type of Mass in most of the western world.
Huh? The Tridentine Mass was established by the Council of Trent in the late 1500s. The pre-1570 Mass is NOT the Tridentine Mass and there are numerous differences. The Tridentine Mass was "based" on earlier Masses, but it's not the same thing. ALL latin-rite Roman Catholic masses prior to 1570 are classified as "Pre-Tridentine Masses"
Huh?
"Outside of Rome in the period before 1570, many other liturgical rites were in use, not only in Eastern Christianity, but also in the West. Some of the Western rites, such as the Mozarabic Rite, were unrelated to the Roman Rite that Pope Pius V revised and ordered to be adopted generally. But even the areas that at one time or another had accepted the Roman rite (see, below, "Middle Ages") had soon introduced changes and additions. As a result, every ecclesiastical province and almost every diocese had its local use , such as the Use of Sarum, the Use of York and the Use of Hereford in England. In France there were strong traces of the Gallican Rite. With the exception of the relatively few places where no form of the Roman Rite had ever been adopted, the Canon of the Mass remained generally uniform, but the prayers in the "Ordo Missae", and still more the "Proprium Sanctorum" and the "Proprium de Tempore", varied widely" <<
You were saying?