This claim, however, is only very partially valid. It holds true in a specific section of the Middle East, namely the contiguous land area stretching from Iran's western borders to the Mediterranean Sea, and taking in the states currently known as Iraq, Syria and Lebanon.
In this area, a single sectarian war is currently taking place. The nominal governments in Baghdad, Damascus and Beirut may claim to rule in the name of the Iraqi, Syrian and Lebanese peoples. But the reality of power distribution in each of these areas shows something quite different.
In each of these areas, local, long suppressed differences between communities are combining with the region-wide cold war between Iran and Saudi Arabia to produce conflict, discord and latent or open civil war.
In each case, sectarian forces are linking up with their fellow sect members (or co-ethnics, if that's a word, in the case of the Kurds) in the neighboring "country" against local representatives of the rival sect.
Let's take a look at the rival coalitions. These are not simply theoretical constructs. The cooperation between the relevant sides is largely overt, and has been extensively verified.
On one side, there are the Shia (and Alawi) allies of Iran. These are the Maliki government in Iraq, the Assad regime in Syria, and Hizballah, the Iranian proxy force which dominates Lebanon.
Both Hizballah and the Maliki government, at the behest of Iran, have played a vital role in the survival of Bashar Assad and his current resurgence.
Hizballah's role is well-documented. The movement maintains around 5,000 fighters at any one time in Syria. They have just completed a spearhead role in a nearly year long campaign to drive the rebels from the area adjoining the Lebanese border. They are also deployed in Damascus.
Assad's Achilles heel throughout has been the lack of committed fighters willing to engage on his behalf. Hizballah, working closely with Iran, has played a vital role in filling that gap.
In addition, Hizballah is working hard to suppress any Sunni thoughts of insurrection in Lebanon itself. Its forces cooperated with the Lebanese Army in crushing Sunni Islamists in Sidon in June, 2013. It also offers support to Alawi elements engaged in a long running mini-war with pro-Syrian rebel Sunnis in the city of Tripoli.
Maliki's role on behalf of Assad is less well-reported but no less striking.
It is first of all worth remembering that the Iraqi prime minister spent from 1982-90 in exile in Iran, and his political roots and allegiances are, unambiguously, to Shia Islamism.
Regular overflights and ground convoys have used Iraqi territory since the start of the Syrian civil war to carry vital Iranian arms and supplies from Iran to Assad's forces in Syria.
A western intelligence report obtained by Reuters in late 2012 confirmed this, noting that "planes are flying from Iran to Syria via Iraq on an almost daily basis, carrying IRGC (Iranian Revolutionary Guard Corps) personnel and tens of tons of weapons to arm the Syrian security forces and militias fighting against the rebels."
It also asserted that Iran was "continuing to assist the regime in Damascus by sending trucks overland via Iraq" to Syria.
In addition, Iraqi Shia volunteers from the Abu Fadl al-Abbas Brigades and other formations have helped to fill Bashar's gap in available and committed infantry.
The Maliki government has made no effort to stop the flow of such fighters across the border – even as it engages in a U.S.-supported counter insurgency against Sunni jihadis in western Anbar province in Iraq.
So the Iran-led regional bloc is running a well-coordinated, well-documented single war in three countries.
The Sunni Arab side of the line is predictably more chaotic and disunited. On this side, too, there are discernible links, but no single, clear alliance.
Unlike among the pro-Iran bloc, only the most radical fringe of the Sunnis cross the borders to engage in combat. There is no Sunni equivalent to the Qods Force cadres active in Syria and Lebanon.
Among the Sunni radicals, the Islamic State of Iraq and Syria (ISIS) group now controls a single contiguous area stretching from eastern Syria to western Anbar province in Iraq, and taking in Fallujah city in Iraq.
Jabhat al-Nusra, the Syrian franchise of al-Qaeda, is now active also in Lebanon. It has on a number of occasions penetrated Hizballah's security sanctum in the Dahiyeh neighborhood of south Beirut.
More broadly, Saudi Arabia is the patron of the Sunni interest in both Lebanon and Syria.
It is currently backing rebel forces in the south of Syria, and pro-Saudis dominate the Syrian National Coalition, which purports to be the political leadership of the rebellion.
It also supports and promotes the March 14th movement in Lebanon, and recently pledged $3 billion for the Lebanese Armed Forces – presumably in a bid to build a force that could balance Hizballah.
But both Qatar and Turkey also play an important role in backing the Syrian rebels, and have their own clients among the fighting groups.
Saudi and Turkish fear and distrust of radical Sunni Islamist fighting groups prevent the emergence of a clear "Sunni Islamist international" to rival the Shia international of Iran.
Still, it is undeniable that cooperation exists among the various Sunni forces in Lebanon, Syria and Iraq.
It's just that it's a complicated and sometimes chaotic criss-crossing of various rival interests and outlooks on the Sunni side, rather than a coherent single bloc.
And finally, of course, there is a single contiguous area of Kurdish control stretching from the Iraq-Iran border all the way to deep within Syria. This zone of control is divided between the Iraqi Kurds of the Kurdish Democratic Party and the Syrian Kurds of the rival, PKK-affiliated Democratic Union Party (PYD).
Once again, it is a contiguous area of control based on ethnic affiliation.
None of this means that the official borders of these three countries are going to officially disappear in the immediate future. The U.S. administration and others are committed to their survival, so they are likely to survive for now, in the semi-fictional and porous state in which they currently exist.
This, however, should not obscure the more crucial point that the entire area between the Iraq-Iran border and the Mediterranean Sea is currently the site of a single war, following a single dynamic, fought between protagonists defined by ethnic and sectarian loyalty.
Jonathan Spyer is a senior research fellow at the Global Research in International Affairs (GLORIA) Center and a fellow at the Middle East Forum.