Why can't the feds force each state to figure out a single-payer system? Our constitution, politics, and culture don't let "the feds" easily dictate such thing

Why can't the feds force each state to figure out a single-payer system? Our constitution, politics, and culture don't let "the feds" easily dictate such things. The federal government can nudge with some mandates and grants (as with the ACA itself), but forced nationalization of industries is hard, especially so when most states (by count) would prefer otherwise. It's also especially hard, if those in favor of single-payer takeover only barely or temporarily have the legislative majorities necessary (again, as with the ACA itself). That much larger and more diverse populations, economies, geographies, and institutions are harder to govern via a working consensus isn't "bullshit", it's a political and historical reality. (How many government shutdowns has the UK had recently?) You can stomp your feet over this, and perhaps wish that some more-powerful central government could just "force" everyone to enthusiastically implement your preferred policy... but that's not the US way. Maybe you could get a single-payer constitutional amendment passed. That'd establish clear legal authority, and prove a broad consensus that would help with implementation. Why don't you try that? I dislike national single-payer (and the baby-step of the ACA) because I don't think it can work well here. It'll have the cost-efficiency of the pentagon, the compassion of the INS, the simplicity of the tax code, and the innovative pace of the FDA. What would be a good decentralizing alternative to this current forced-march towards unprecedented-scale nationalization? Leave more details to the states. Use national action mainly to undo existing distortions, like medical cartels/protectionism and the tax-preference for non-portable employer coverage. And, provide direct payment assistance to the neediest/sickest, rather than new regulations on the shape and cost of policies for everyone.