Perhaps the point is that those lower levels of government are inefficient and wasteful because of over duplication of effort?
You have it backwards.
For obvious reasons the state governments know what their states need rather than a massive government sometimes thousands of miles away.
The Federal government does not have the infrastructure and ability to directly control 50 states. Its why armies are not composed of just lowly privates, and high ranking generals. There are captains and sgts and corporals and colonels. Delegation is critical in any system. its too much for one person.
Why have 50 governments doing the job that one government can do? That one government through economies of scale can offer greater efficiencies.
because one government can't do it?
because the 50 governments are doing the job for 50 states. to each their own in fact. Hawaii isn't managing Maine, for example. So its not 50 governments doing the job of one federal government in the first place. if you think of a state government as a "person", and the sate is their "job", we have 50 different people doing their own job, but for the same "boss" (boss being the federal government) your proposal would be either eliminating those people and having the boss do things one at a time, or simply making them all "bosses" that then go off and try to do whatever job that pops up that they don't, if ever understand.
That's no way to run anything. plus its not democratic.
And the federal government has almost never been capable of greater efficiency, even with state govs running their own states. You really think the federal government which can barely keep its own economic affairs in order will suddenly be able to make 50 separate economies run better than the states that were running them? State governments pass laws. Laws that may work for their state but not another as well. What is legal in one state is illegal in another. along with a different set of standards. Example? minimum wage is different in Washington ($9.19) than it is in Texas ($7.25) The standard of living is more expensive. There is a federal minimum set, but states will offer more due to the unique circumstances of that state. I have even live in a state where it varied by city. the minimum wage was $5.50, while only 60 miles north it was almost double that at $12 because that city was tourist haven so everything was hellaciously over priced. If you expect the federal government to have that kind of nuance and knowledge I have bad news for you.
There is also the danger of under representation. If you are a small state by population, you will be paying federal taxes while getting very little federal help. Lets say I have a pot hole outside my apartment. Do I call Washington DC to fix it or do I call the local government? Is there a Federal Bureau of Potholes? and if so, when I call am I put on a "to do list" behind 20,000 other people in 50 states who also need their potholes fixed? When 6 months have gone by and nothing is fixed because I am being ignored, who do I complain to? I have no representation. Who do I threaten to oust by not voting for them? Where is City Hall? Do I have to fly to DC to plead my case if so, am I the 22,567,234 in line to be heard? Do we really need a giant government to even fix a pot hole in the first place? Maybe he has other bigger problems to solve? I just end up fixing the pothole myself a year later. Eventually myself and others decide we are tired of paying huge taxes so we can fill out our own potholes anyway and decide we are no longer going to pay for service we are not receiving. We will have a local tax to fix local problems based on what we feel is most necessary by a majority vote of local citizens. IE a local government.
In short beyond just the impossibility of the suggestion, there are philosophical reasons as to why it is a bad idea. The US is built to be anti-Tyrant. One giant unwieldy government is how tyrants are made, as the only way to get anything done is to strictly curtail and control the population and make them as single minded as possible. Its the same reason why there isn't "Just one big Europe" the populations though sometimes similar are not homogeneous enough to work toward the same end. Economically Germany is a powerhouse, Greece a disaster, etc.