One aspect of US taxation and funding that seems wildly out of step: Primarily local funding of schools. Way to build inequality into the system!
None of these seem like very close comparisons to the US model. There isn't the same legal independence in Spain on a number of matters, from what I recall, but I'll see if I can find a source that provides a direct comparison. For starters, Spain could actually issue centralized coronavirus restrictions and has only recently devolved this to a limited degree to the autonomous communities.
A few EU countries may be more relevant, but I think the closest comparison I've found so far is with Switzerland where I currently live. However, the federalism in the US seems to involve a lot more infighting with frequent lawsuits between state and federal agencies.
The USA is a very strange mix of hyper-first-world and second/third-world, and a lot of it has to do with how taxes are raised and spent.