potato famine is why bostonians and new yorkers talk funny,
romans implementing tariffs because they were total retards when it comes to the economy is directly responsible for feudalism and the 1000 years of bullshit that caused. it's the reason europe looks the way it does today and has subsequently shaped all european history, which affects american history.
the byzantines lost their empire because one dude backstabbed the basileous for sassing his wife and let a whole army of seljuks through the mountains to flank. result? ototman empire, islamic middle east, death of the roman empire, and everything related to that region today is the result of that.
too vague?