Given what we've said so far, it would be tempting to say the island represents "America." After all, most of the island's inhabitants symbolize American political figures, groups, or concepts, and the island's DHARMA system symbolizes America's democratic system.
But remember, the castaways and DHARMA Inititive aren't the first people to live on the island. They're just the ones who live there now. Other people from a wide variety of civilizations have lived there in the past. People from Britain resided there, arriving via the now-shipwrecked Black Rock. The Greeks have left their mark on the island, what with the Greek writing on Jacob's tapestry. Ancient Rome must have made a visit, given the island's prevalence of latin-speakers. And the statues and heiroglyphs are most likely the work of Ancient Egyptians. The presence of those other civilizations suggests the island isn't "America" but rather something that America, Britian, Ancient Greece, Ancient Rome, and Ancient Egypt have in common. Most likely, the island symbolizes something currently held by America but once held by Britian, Ancient Greece, Ancient Rome, and Ancient Egypt.
Given that Britain, Ancient Greece, Ancient Rome, and Ancient Rome were once empires, and America is now the world's sole superpower, it would safe to assume that the island symbolizes "superpower status."
In other words, the island doesn't symbolize a physical location, it symbolizes a geopolitical position. And the communities in possession of the island at any given point in time would symbolize nations holding superpower status at that point in history. Likewise, communities trying to acquire the island for themselves would represent nations trying to acquire superpower status.
It's can be a tricky concept to grasp, but it's an important one. They best way to think of the island is to use the metaphor of a crown: Just as the person wearing the crown is treated as king, the community occupying the island is treated as a superpower.
I won't be exploring the idea too deeply here, but we'll definitely explore it later, during Season Six, because its a fascinating political topic. For now, here are a few tips to help you better make sense of the island's symbolism.
A few ways in which the island resembles "superpower status"
SuperpowersThe island has "super-powers". Particularly powerful nations are known as "superpowers."
ExceptionalismThe island is regarded as exceptional. Superpowers regard themselves as exceptional.
Violating lawsThe island violates universal laws (of time and space) in ways other islands cannot. Superpowers violate international law in ways other nations cannot.
Being hard to reachReaching the island can be a difficult and painful process. Acquiring superpower status can be a difficult and painful process.
Losing touchWhen you are on the island, it's easy to lose touch with the outside world. When you acquire superpower status, it's easy to lose touch with the outside world.
Internal conflictsThe islanders' fiercest battles are with other islanders. Superpowers typically collapse due to internal problems, not external attacks.
Moving around the globeThe island moves to different points on the globe at different points in time. Superpower status has moved to different points on the globe at different points in history.
Occupation by past empiresThe island was previously held by visitors from Britain, Ancient Greece, Ancient Rome, and Ancient Egypt. Superpower status was previously held by nations including Britain, Ancient Greece, Ancient Rome, and Ancient Egypt.
Current Occupation by AmericaThe island is currently held by characters with America-related symbolism. Superpower status is currently held by America.
The island's three communities
Even though they act like separate factions, the castaways, DHARMA Initiative, and Ben's camp are actually three sides of one community. Together, these three groups symbolize most of the figures, institutions, and concepts that make up America's political system. That means that whenever one or more of these groups is shown to be occupying the island, we can assume that Lost is portraying a time when America is a superpower. And if none of those groups are shown to be on the island, we can assume Lost is portraying America's superpower status coming to an end.
The communities' different times of arrival
If they're one community, why do the castaways, DHARMA, and Ben's camp arrive on the island at different times? It's because the three groups' real-world counterparts became interested in America's superpower status at different times.
The members of the DHARMA Initiative are the first America-related characters to arrive, because they symbolize the idealists who established and maintained America's original ideals. They held the belief that America might one day use its superpower status to "save the world", but they were also concerned that, without the right systems in place, America could fall apart just as previous superpowers did. Just as the DHARMA Initiative has been dwelling on the island for years, its real-world counterparts had long "dwelled" on the risks and benefits of America being a superpower.
Ben and his recruits arrive later than DHARMA but long before the castaways. At the time of the 9/22 plane crash, they have already been on the island for several years. By having Ben on the island at the time of the crash, Lost is showing that, at the time of the 9/11 attacks, Ben's real-world counterparts -- Neoconservatives -- had already been thinking about America's superpower status for years. Just as Ben has long advocated using the power of the island to eliminate his enemies, his real-world counterparts had long advocated using America's superpower status to remove the leadership of enemy regimes. In other words, Ben didn't need the crash to bring him to the island any more than his real-world counterparts -- Neoconservatives -- needed 9/11 to get them thinking about America's superpower status.
The castaways are the last to arrive. They have no knowledge of the island until 9/22, when they are forcibly delivered to it by the plane crash. Here, Lost is suggesting that the castaways' real-world counterparts hadn't given much consideration to America's superpower status until forced to do so by the 9/11 attacks.
Richard Alpert appears to be a permanent fixture on the island. That's partly because he represents Dick Cheney, who has been in the US Government for decades. But its also because he represents a type of power-broker present in the government of every superpower since the beginning of human civilization. Richard is a savvy political opportunist. He doesn't help the island's new islanders build their societies -- he waits in the jungle until the society has been built, then he usurps it. And once he usurps it, he turns it into the kind of society he prefers, one based not on ideals but on power. This behaviour reflects the modus operandi of those ever-present political players who wait in the wings while idealists build a society into a superpower, then usurp the reigns of power and use the government for their own ends.
Sharing the island
Just as superpower status can be held by more than one nation at once, the island can be occupied by more than one community at once. Right now, the castaways (together with Ben's camp and the barely functioning remnants of DHARMA) are the main force on the island, reflecting America's position a the sole superpower. This will most likely change in Season Six when, if my predictions are correct, an Asian character will offer much-needed assistance to the castaways (just as China offered much-needed financial assistance to America), and then move onto the island (just as China has started moving into the position of superpower), causing some of the castaways to fear that, if they can't compete aginst him, they'll lose the island to him completely.
Even though they don't give it much thought, the castaways have actually been sharing the island with someone else for sometime now: reclusive but resourceful Danielle Rousseau, who has been sending out a call for others to come and assist her. Danielle's call for others to join her on the island represents jihad-driven islamic fundamentalists (such as Al Qaeda) calling for other muslims to join them in restoring the muslim world to superpower status.
Charles Widmore desperately wants to return to the island. This symbolizes the government of Iran wanting to return Iran to superpower status. Ben is fiercely opposed to Widmore's return to the island, symbolizing Neoconservatives' fierce opposition to Iran aspirations of acquiring superpower status.