Using Arabic, English, and French sources, and engaging Middle East and Cold War historians, this article makes a threefold argument. First, in United Arab Republic (UAR)–Syria, Jordan, and Lebanon, the 1958–59 explosion of domestic and regional tensions triggered state-formation surges. Second, these formed one process, which made those states more alike, with state-led socioeconomic planning playing a key role. Third, that process partook of a global Third World trend intersecting with the early Cold War. I draw three conclusions. Although existing scholarly readings that the events of 1958–59 in the ArabMiddle East formed a crisis but not an ideological or political watershed are correct, from the viewpoint of state formation this crisis was a milestone. Moreover, UAR–Syria, Jordan, and Lebanon had persisting affinities and shared regional positions—notably, the fact that all were sandwiched between the unstable poles of the Arab state system, Iraq and Egypt—that shaped their individual postindependence histories of state formation. Last, Washington's low-profile involvement in this state-formation surge illustrates how domestic sociopolitics and regional geopolitics—including the UAR's peaking popularity and influence in 1958–59—affected U.S. policy in the Cold War postcolonial world.