Between Europeans and the Americans, the Americans lacked pack animals and a region which could create bronze. Also, due to the European exposure to pack animals and other reasons, lethal diseases went mainly from Europeans to the Americans instead of the other way around. It also isn't a good sign when a foreign civilization has the technology to show up at your shores while your civilization doesn't.

Between Europe and the rest of the Old World, Europe wasn't able to colonize the rest of the old world until after the Industrial Revolution started. The Industrial Revolution started in Europe mainly due to increased state competition compared to other parts of the world and higher labor costs making capital investments worth it.