Believe it or not the first World War didn't actually begin when America joined in. WW1 was a colonial war in which the central powers (especially Germany) wanted to increase their colonial powers and Great Britain wanted to maintain the status quo (the British Commonwealth being the largest empire the world has ever seen). All the European powers had isolationist policies that restricted trade to their own respective empires. The desire for gain a larger portion of what seemed at the time to be an infinite expansion of available resources led to conflicts between these enormous colonial empires. So you are right that imperialism was a cause of WW1, but if the empires had been willing to trade amongst each other there would not have been such a level of competition between them. That's a very brief explanation, hope it answers your question for you.
I know that, hence the second paragraph of my previous post.
In any event, while your point about trade is well-taken, you can hardly call imperialism an isolationist policy. Imperialism is a policy which inevitably and obviously will lead to entanglement with other nations. If we can agree that the creation of European Empires is largely what caused the first world war, then by connection it was caused by
expansionist, not isolationist, tendencies.
For federalism to exist there must be multiple local governments and one central administrative one. If there are multiple local governments where just one is enough then that obviously means there are an excess of bureaucrats and a confusion of laws between states. Thus, federalism is less efficient because you have more people doing exactly the same work. Do you honestly believe the varying laws in different states represent the true wishes of those state's citizens? Wealthy citizens just travel to a state that legalises something they wish to do while poorer ones are forced to either do it illegally or not at all. Admittedly there are some laws that are genuinely different, others (the vast majority, such as road laws) are just needlessly complicated by federalism.
There's fallacy in that argument- yes, you have people doing the same TYPE of work, but I can guarantee that the mayor of New York is doing different work from the mayor of LA. What's more, it's clear that the state legislature of Alaska has different priorities on what kind of laws to pass than that of Hawaii.
For instance, let's take the latter case. A SINGLE federal government would have to deal with issues pertaining only to one region ONE THING AT A TIME. Do you understand how much this would muddle the legislative process? Let's say the issue involved the hunting of caribou or something specific to Alaska. You're wasting the ONE and ONLY legislature's time with dealing with an issue that only affects one state! Now imagine if you get 50 such specific issues. Pretty soon the legislature is clogged with these nitpicky issues which only cover certain parts of the map. That's INEFFICIENT! No, far better that we have state governments. That way, all 50 of those state-specific laws can be passed at once instead of one at a time, and they won't get in the way of laws which affect the entire geography of the united states (which is what the feds are supposed to do.)
Isolationist policies, at least in the US, didn't start until after WWI when the American people didn't want to be dragged into a massive conflict because an ally was attacked. These policies ended on Dec. 7, 1941 for all intents and purposes.
I'm gonna disagree on that one. America had been isolationist since basically day one, with a few exceptions, and then a major break in policy on the parts of our well-known imperialist presidents, but mostly the post-WWI streak of isolationism was a result of what you said, a desire not to fall into the trap that europe did in making a bunch of alliances.