Flying Flags in America

There are lots of national flags flying outside houses here. I am not entirely sure about why, but you can buy flag flying kits from the hardware store with a flag, and a stick, and the mount to attach to your front porch uprights. I think the flag is very deeply tied in with national pride.
We bought our car from a navy guy, who flew the flag of his regiment/company out the front of his house. Flying regimental flags and US flags together is not uncommon. I also know that since 9/11, firefighters especially, have been more patriotically associated (and therefore, more likely to have flags?). This may be because 9/11 was seen as an act of war by some, and the firefighters took heavy casualties trying to rescue people.

We have had three public holidays so far that encourage the flying of flags -
Presidents Day/ Washington's Birthday (Feb 17th) (not a public holiday for hubby)
Memorial Day (May 26th), also seen as unofficial start to summer
Independence Day (July 4th)
There were also observances for the D-Day landings in France in WWII - the USA forces were a large part of the initial landings, and a lot of their men died as a result.
On May day in Annapolis, people are encouraged to decorate their homes in red white and blue (and flags, and flower arrangements).
I'm also pretty sure that on Veteran's day (November 11th) and Thanksgiving (November 27-28th) there will be flags!

The American flag is deeply tied into the birth of the nation - with the national anthem 'The Star Spangled Banner' being penned after Francis Scott Key saw a flag flying over Fort McHenry after particularly heavy bombardment by the British during the Battle of Baltimore in 1814. It has changed as the union grew - increasing the number of stars and stripes.
In fact, after warring with the British, the Americans warred with each other, and this was the flag chosen after the dust settled. So maybe the fact that they chose their flag, and fought for it (the winning side atleast), influences how they feel about it?

I'm not sure if any of this helps to explain why you can walk through neighbourhoods today and see flags on several houses on every street, and over restaurants (and not just in front of official state buildings).
 (final note - this is a 'Navy' town, so flag flying might be more common here than in other American towns)