Comment by Clubber

This is a good summary. The US was designed similar to the EU; each "state" is autonomous, but some things are shared, like currency, etc. Allowing frictionless movement between states is also paramount (and explicitly defined).

The logic being, if a state starts to get out of control, you can just move to another state. This allows states to experiment with various laws specific to the population.

Most of this was undone with the Civil War. As abhorrent as it was, the federal government had no legal power to ban slavery outside a constitutional amendment. The 13th-15th amendments actually banned slavery after the war, not the Emancipation Proclamation. Today, the federal government bans whatever it pleases and uses the commerce clause to skirt the constitution.

Take the drug war for example. Because a group of drugs was federally banned, states were powerless to do anything about it. I think most people would agree that federally banning all drugs ended up being a terrible idea and ruined many lives and families over the course of it's execution. It continues to do so today. If the constitution was actually followed, each state can determine which drugs it would allow. As far as I know, Colorado hasn't devolved into a cesspool of depravity since it legalized pot. Imagine all the hell that could have been avoided if states were allowed to decide which drugs to ban rather than the federal government.

Of course a strong federal government has some plusses as well. It was hotly debated during the country's inception, but the ultimate compromise all the states agreed to is what we got.