1) there were way more native Americans then Europeans
2) A trained musketeer was not that superior to a trained archer, archers can fire volleys much faster
3) shouldn't Europeans be *just* as susceptible to Native American diseases as the other way around?

1) the American people were not nearly as densely populated as Europeans were at this time, thus making the number's difference between the colonists and the Americans closer to equal.
2) The Americans were very tribal and thus did not present a united front against the Colonists, in fighting and cooperating with the colonists assisted the colonists in taking over the Americas
3) The American's didn't fight back, they attempted to work with the colonists and be all buddy buddy until the evil Europeans betrayed them (yeah, I suspect this view is also biased, but I don't know)
4) the Americans were recovering from their own epidemic about the time that the colonists arrived, thus thinning their numbers out (not sure where I heard this, but swear I heard it once?)
5) The colonists technology included better understanding of tactics and fighting as a cohesive unit, which allowed great tactical victories despite otherwise equal forces.