The correct answer to this open question is the following.
In today's economy, countries have far more economic ties with other countries than they did 100 years ago. Why then, might political unrest in the Middle East today affect the economy of other countries?
Because in the Middle East are large oil deposits that are the motive of conflicts, confrontations, and wars, due to the fact that oil still is one of the most valued goods for all countries.
Developed countries have economic and political interests in this conflictive region, which are worsened by the fact that Jews and Palestine are disputing territories even today. Yes, the legendary conflict between Jerusalem/Israel against Palestine and the Arab nations.
That is why these conflicts directly affect oil production, which impacts the international economy and the stock markets of the world.