I think some historical "what if?" questions are not really plausible. One cannot really ask what the world would be like because a) Rome held onto its power for some 1100+ years and b) it had such a fundamental influence on Western Civilization. We really don't have anything to compare it to and we don't know if some alternative civilization would have risen to Rome's extent and assumed its leadership role in politics, military, the arts, and other areas. In other words, any answer we could give would be mere imagination with little evidence to rely on.
Of course a couple hundred Spaniards with rifles, horses, and excellent political skills pretty much owned all the South American civilizations too. Possession of a specific technology is not important but I do not see how the Western world as we know it would exist absent Rome. Don't forget the Greek influence either. Of course, Rome was essential to the Western World.
Don't forget the Greek influence either. Of course, Rome was essential to the Western World.
What if Rome didn't conquer Greece ? Would Greece had a deeper influence on our civilisation without Rome ? I'm refering to the Antikythera mechanism, the machines built by Archimedes (brought to Rome after the death of Archimedes at the siege of Syracuse in 212 BC), Science, Philosophy, Religion, Politics, Arts and so on...
First of all, I don't know how Rome would have operated without having conquered Greece, since the Roman Empire extended way beyond Greece on all sides. However, even if we assume for the sake of argument that the Roman Empire existed with an “island” of an independent and free Greece in the middle of it, it wouldn't have mattered; by the time Greece was conquered, Greek culture had already been spread through what we now call the Hellenistic world by Alexander the Great and others. So now, we would have to change our hypothetical even more. What if the Roman Empire existed without having conquered the Hellenistic kingdoms (i.e. basically the entirety of the east, and part of the southern Mediterranean, would never have fallen into Roman hands)? For one, this would have meant that the Roman Empire was far smaller than it actually became. Even so, I think that Greek influence would have pervaded Rome and the west; it was actually the conquest of the city of Syracuse (on the Italian mainland) in the third century B.C. that led to the adoption of Greek art and architecture by the Roman Republic. Even aside from this, the Roman Republic and Empire would undoubtedly have traded with the Hellenistic kingdoms and would have decided to emulate Greek culture through these activities. In the end, I don't think that Greece would have influenced Rome much less had Greece or the Greek world not been conquered.