A Few Facts Concerning the Last Great Superpower and a Few Questions Those Facts Engender

Since 1991, the United States has been engaged in an undeclared war with Iraq.

Approximately 169,000 square miles, Iraq is roughly the size of the state of Washington (172,000 square miles).

But it is crowded: in 2012, the population of Iraq was roughly 33.7 million souls--slightly less populous than the state of California (in 2012, roughly 36.7 million souls).

The GNI per capita in 2011 for Iraqis (in U.S. dollars): $2,640.00
The GNI per capita in 2011 for Americans (also in U.S. dollars): $50,860.00

And yet, I repeat: since 1991, the United States has been engaged in an undeclared war with Iraq.

What is this war (and, I repeat, since Congress ceded its Constitutional control over the war-making powers to the Executive Branch after the Second World War, it is an undeclared war) all about?

What are its objectives? What does the United States hope/expect to gain from a (now generational) conflict with a small, crowded country in Mesopotamia?

How does this small, crowded country represent a threat, military or otherwise, to the Last Great Superpower?