How come the Europeans were so much more technologically advanced than the Americans? What led them to be so?

well horses aren't native to the americas so that was kind of a disadvantage right off the bat. Native tribes had no pack animals or beasts of burden meaning that they would have to move everything by themselves (though some did use dogs to pull sleds dogs can't exactly carry much). It is also a misconception that they had "just" discovered farming agriculture had taken root at around the same time as it did in afro-Eurasia but the crops and the style of agriculture were radically different from what the first european settlers were used to.

You also don't seem to realize that the things that made Europeans so good at exploring and conquering (compasses, triangular sails, guns) weren't european inventions at all but taken from asian and muslim cultures.

You are also overlooking the amazing feats of engineering accomplished by meso american cultures like the Aztecs, Mayans and Incas all accomplished without written language and without pack animals and most importantly without aliens.