Or look to the United States, which once had 20,000 passenger trains roaring down a quarter-million miles of active track every day: a dynamic country fueled on the coal and steam of locomotives. After World War II, a powerful coalition of Texas oil interests and Detroit auto manufacturers helped push through the Federal Highway Aid Act of 1956 that jump-started the interstate highway system. Railroad companies were encouraged to dump passenger service, and this — among other factors — helped bring massive structural transformation to the country: broadening the footprint of suburban sprawl, addicting Americans to petroleum, changing agricultural and retail patterns and, as a footnote, sending the once-mighty American passenger train into the perpetual nursing home of Amtrak.

Other global examples, both historic and recent, show how state metamorphosis manifests in the railbed. Russia became a bicontinental power by extending its rails into Siberia. Benito Mussolini famously took credit for Italian rail upgrades. The British unified thousands of principalities in colonial India not through language but through railways, and when the government of former Prime Minister Manmohan Singh sought to ramp up the economy in the mid-2000s, it cut hiring quotas at Indian Railways and promoted round-the-clock freight loading. China sought to hit six percent growth targets through the last decade by building a stupendous $508 billion network of high-speed trains knitting together its major cities. Last year, Kenya opened the Madaraka Express between the port at Mombasa and the capital of Nairobi that can carry 22 million tons of cargo a year, strengthening its dependence on imports and deepening its reliance on Asia.

The calls to reform France’s SNCF is partly coming from the outside — the European Union requires members to open railways to competition by January 2019. Still, Mr. Macron is taking aim at an institution that — for all its glories and faults — comes close to representing the soul of France itself, a representation of the permanent state indifferent to the winds of politics ever since Emperor Napoleon III provided a state guarantee of interest to bondholders in 1852, and instructed Georges-Eugene Haussmann to give the marbled palaces of railway stations an honored place in his redesign of Parisian boulevards.

Lines radiated outward from the Gare du Nord, Gare de l’Est and Gare d’Orsay, among others, creating a Paris-centric concept of the hexagonal nation that persists today: The historian Jules Michelet perceived it as a grand tool of unification. “The chateau represents pleasure, the caprice of one man; the railway is for everyone’s use, bringing France together, bringing Lyon and Paris into communion with one another,” he is reported to have said after a ride to Versailles. Gustav Eiffel made himself a celebrity engineer with railway bridges before he ever attempted a tower, and France remade its countryside with suburbs anchored to railway stations.

The heavy hand of Paris brought distinctively French touches: padded seats even in third class, an unwieldy timetable the size of a dictionary, the grandeur of the high-speed TGV, and a class of civil servants who call themselves cheminots with essentially a job for life and guaranteed sick leave, which created the old French joke that working for the railway must be dangerous because its employees are always getting ill.