But it was entirely their fault. It was their vanity and lack of foresight what destroyed them.
(A lesson contemporary politicians should better remember well...)
Oh boy, where's Masada when you need him?
Have you ever seen a llama? I suppose that is true for Oceania, but the Americas lost out for more diverse reasons. Some theorize that the delay in American civilization had to do with corn taking longer to become suitable for large scale agriculture the way wheat was in Europe and the Near East and rice was in the Orient.
Disease was obviously a huge factor, as smallpox and company were far more effective at destroying American empires than any European army was. Syphilis just wasn't as deadly.
Sugar and alcohol also didn't help, although these came later (and tobacco has probably been more damaging to Europeans than alcohol has to Americans).
The Americans (pre-1492 Americans, I mean) definitively lost for one reason and one reason only, and that's disease. Sure, other factors were at play, but it was Afroeurasian diseases that ended any chances that American societies, however large or sophisticated or isolated, can successfully stand their own against Eurasian societies. Americans successfully adapted to and adopted Eurasian technology almost everywhere they encountered them, but waves of epidemics reduced all but the most populous to scattered bands unable to resist the sheer mass of Eurasian colonisation.
Absolutely! Neither ever looked to the New World, really... and Spain/Portugal could stop them if they'd tried, with Gibraltar...
The Ottomans did try to contest the Portuguese for mastery of the Indian Ocean, and was actually partially successful in diverting trade towards Istanbul for about a century. The Ottomans and the Portuguese actually lost their grounds in the Indian Ocean at about the same time for the same reason; they were grossly overstretched.
This is especially true for England and Holland... both were somewhat stifled geographically (but still performing decently well), and this just blew the doors off the situation!
Holland with its many waterways (important for agriculture, power, defence, transport, trade) wasn't actually disadvantaged at all. England sits on top of one of the largest and most easily accessible coal reserves in the world, with a relatively easily defensible position - IMHO it's the luckiest country in Europe. Bearing the bloody days before and after the Norman Conquests, the sporadic wars with Scotland (worse for Scotland than for England, I think), and occasional civil wars, the English didn't often experienced the sort of near-constant, near-total, shifting warfare that plagued continental Europe and Asia.