How do Obama's efforts to try to ease the financial stress in the US help Europe?

The world today has an economy that is very highly
interconnected as a result of globalization.  Therefore, stress in one country (so long
as it is a major country) can put great stress on other countries as well.  This means
that Obama's efforts to fix the US economy have, to the extent that they have been
successful, helped Europe as well.

The United States is
still the world's largest economy.  As such, it is a major trading partner for many
other countries in the world.  Financial stress in the US decreases US demand for
products from other countries.  This is bad for Europe as well as for other regions of
the world.  The US dollar is also the major reserve currency in the world.  Stress in
the US economy hurts the value of the dollar and, thereby, Europe's reserves of
dollars.

The interconnectedness of the world economy means
that financial difficulties in a country as big as the US will lead to problems in other
countries.  By easing problems in the US, Obama's efforts help other countries such as
the countries of Europe as well.