Having examined liberty as it relates to governments in general, I delve now into particulars.
I believe that liberty can be secured in many different forms of government (including monarchy, oligarchy, theocracy, and democracy) and economic systems (capitalism, socialism, and yes, even communism). However, long experience--and wise Founders-- have demonstrated that democratic, capitalistic governments best foster the principles of liberty in our modern world. (More about capitalism later.) This is not to say that other forms of government or economics cannot function in liberty, just that they have not in recent memory. Nor should this be taken as a chest-thumping declaration that our own current brand of democratic capitalism is beyond reproach; there are certainly improvements to be made in both form and practice.
That being said, I firmly believe that, think what you will about our country, the American experiment has resulted in more liberty for the whole of mankind than any other political development in all of history. Since that bold declaration of individual empowerment-- the idea that government derives its power from the consent of the governed-- freedom has been on the march; the world as a whole enjoys more liberty now than at any point in all of history.
I love America, with its beautiful diversity of land and people. But even more, I love what America stands for, what it represents-- an idea. From a the tall, copper woman in New York harbor to the last line of the our national anthem, America is a symbol of liberty. I love the image of a rag-tag group of upstarts standing up to an empire (Star Wars, anyone?) covering two-thirds of the globe and declaring, "Don't tread on me!" and "Give me liberty or give me death!" America, maybe more as an idea than an actual landmass, is truly "the last best hope of earth." (Lincoln said that prior to the Emancipation Proclamation. "In giving freedom to the slave, we assure freedom to the free -- honorable alike in what we give, and what we preserve.")
To quell any accusations of blind nationalism, I fully recognize that we all too often fail to live up to our great heritage. I also would like to say that too much is made of America being "the greatest country in the world." For me, this is reminiscent of C.S. Lewis' admonition, "Pride gets no pleasure out of having something, only out of having more of it than the next man." America has no monopoly on greatness. That which makes America great-- its dedication to liberty-- can, has, and hopefully will continue to make other nations great. We should strive towards that end, rather than revel in comparative liberty.
Furthermore, if America is to remain great, we must cling to liberty as our life blood. Without liberty, we are lost, as a nation, and as individuals.