If you count FVEY, CAFTA/NAFTA/USMCA, NATO, NORAD, NEXUS, and their other treaties and agreements, Canada and US are closer to what a federation is and should be than what the US is by itself (with the feds heavily meddling in internal state affairs and strong arming the states into staying within the federation).
Sidebar: It might be interesting to study the origin of the root word via history: Foederati. tldr: The Roman Republic became an empire due in large part to its uneven treaty and tension with the foederati which led to a civil war that greatly destabilized the republic and precipitated its transformation into an empire. A few centuries later, one of the foederati, Alaric and his Visigoths sacked Rome and precipitated the fall of the Western Roman Empire (which was symbolically marked by another foederati leader: Odoacer at Ravenna).
Sidebar: It might be interesting to study the origin of the root word via history: Foederati. tldr: The Roman Republic became an empire due in large part to its uneven treaty and tension with the foederati which led to a civil war that greatly destabilized the republic and precipitated its transformation into an empire. A few centuries later, one of the foederati, Alaric and his Visigoths sacked Rome and precipitated the fall of the Western Roman Empire (which was symbolically marked by another foederati leader: Odoacer at Ravenna).