Most other federations have formal mechanisms for ensuring fiscal equity between their federal constituents – Australia has the Commonwealth Grants Commission, Canada has its Equalization Program, Germany has the Länderfinanzausgleich, Switzerland has Nationaler Finanzausgleich, Brazil has the Fundo de Participação dos Estados, Mexico has Participaciones Federales, Argentina has the Régimen de Coparticipación Federal de Impuestos; the UK is a devolved unitary state not a federation, but it has the Barnett formula – the United States is unusual in being a federation without formal fiscal equity mechanisms, although its informal mechanisms (progressive taxation, social security, welfare, Medicare/Medicaid, Congressional earmarks and pork-barrelling, etc) end up achieving much the same end with less transparency in the process.

And I don't know why people keep on comparing the US and the EU. One is a federal nation, the other is a supranational entity. Other nations with federal systems–Canada, Mexico, Australia, Germany, Switzerland, Argentina, Brazil–are better comparators–comparing an apple with (smaller) apples instead of with an orange.

Progressive taxation and welfare don’t achieve the same end, because they’re directed to individuals rather than the government. Mississippi can’t use social security payments to build infrastructure.

Also, programs like Medicaid aren’t as redistributive as you might think. For example, Mississippi gets less federal medicaid spending per capita than Massachusetts, New York, or California, despite being the poorest state: https://ffis.org/wp-content/uploads/2024/10/SA23-01.pdf (p. 4). In terms of federal K-12 education funding, Mississippi receives about $3,000 per student, but California receives almost as much, $2,750 per student: https://educationdata.org/public-education-spending-statisti.... Utah meanwhile receives only $1,300 per student, while Alabama receives about the same as New York, at $2,400 per student.