Which Of These Was A Reason The Us Adopted A Policy Of Isolationism Before World War Ii

If the US was really isolationist prior to World War II, why did it have a Pacific fleet with three aircraft carriers in it?Were Japanese fears of US expansionism legitimate?

The rumors of the US's isolationism have been greatly exaggerated. First and foremost, the US maintained a regional hegemony in the Americas and Pacific Ocean ("hegemony" and "isolationism" cannot ride in the same cart at the same time -- they don't get along).  Some of the US's policies were, by overlap, enforced by France and the UK, so the former forced the latter two to foot the bill.  Not a bad gig for the US tax payer.This means that France and the UK kept Europeans out of our backyard. The oceans kept all but the bravest contained in their native land masses. The Pacific Ocean had enough islands to hop within striking distance of the US and that warranted a powerful navy, which the US maintained for precisely that issue (the US had eight aircraft carriers prior to WWII, it ended the war with >30 large carriers & >70 escort carriers; over 100 on order). Complicating matters, the US had always seen the vital importance in maintaining a modern, blue water navy. Starting in the 1860's the US took note of the fact that empires that failed to own the seas ended up in the ash heap of history. The US maintained sufficient naval power to contain any enemy away from the mainland of the US until it could leverage the large population and massive industry to arm for war. The lone exception was the British empire. It had the power until 1880 to hurt the US considerably if it really put its heart into it. It never bothered (too expensive:  the British Empire was always a company with a monarch and a navy -- the source of its greatest success).  This was still uncomfortable for the US, so when World War II broke out, the US leveraged the British need for aid to gobble up bases and put the Empire in hock to the US treasury. But the US was never isolationist. Citizens were largely provincial, but the US government was very global after William McKinley gobbled up the last embers of the Spanish empire. What the US was, was ideologically unaffiliated and disinterested.  (But even that is a misconception -- the US was passionately interested in preserving the UK as a cousin democracy in Europe).

Why did the USA return to the policy of isolationism after ww1?

For one thing, we've always felt it best we keep these continentsto ourselves and stay out of entanglements overseas. That part is as old as Washington. But more importantly, we paid a high price in wwi — just nowhere near as high as the other belligerents. Their investment in blood and treasure demanded specific outcomes, hard and fast results they believed would prevent a repetition of this terrible carnage. The US sought to impose a workable solution on all parties and then just to work with the victors and fially just to get out. So much, then, for long-standing policy and diplomacy. Finally, there was the factor of personality. Had Woodrow Wilson not suffered a debilitating stroke, he might have bullied or persuaded Congress to follow through on a policy of involvement, but of course he did and there was no one else willing to carry the torch.

If the United States adopted an isolationist policy today, abandoning all foreign military installations, what would likely happen in respect to international politics?

As tempting as this sounds to a lot of people, it would be problematic. Regardless of what you think about the role that the United States plays in the rest of the world, a lot of the security that we have seen around the world can be attributed to the projection of US military power. If this were to happen relatively rapidly, lets say over the course of a year or two, here are some predictions that I would have.Alliances with Israel, Japan, South Korea, and NATO would all break down, as the US could no longer be credibly relied on as an ally. The likelihood of conflict in these regions may increase over the coming years. Realistically, there may not be a tremendous threat to the US homeland in the immediate sense. If it keeps a large Navy as it has had for centuries, the nature or the United States geography would keep it well protected from traditional military threats. It would be difficult to say the effect it would have on terrorism. There would be less ability to collect intelligence around the world and forecast future attacks. However, al Qaeda's main grievance with the US stems from its military bases in Saudi Arabia. All in all the terrorist threat, especially from the Middle East, would probably decrease.The United States' bargaining power in international disputes, would decrease. The US keeps military installations around the world for two main reasons (that I can think of). Firstly, it deters other countries from attacking the US or its allies, or otherwise taking actions to destabilize the international system. Secondly, it project power and influence outward so as to have leverage on other states. It gives the US the ability to get countries to do things they would not otherwise do. Essentially, there is a reason that the United States posts so many military installations around the world. It is trying to maximize the security of itself and its allies. This is not to say that the US could not make significant cuts to its military presence around the world, or that it is always a force for good. It's not. Its a force for protecting the United States and its interests.

Why was US's foreign policy characterized by interventionism after WW2?

Lots of reasons. A few important ones include the following:Europe was basically bulldozed to the ground after WWII, and the soviets had expansion plans, or thought that the West had expansion plans so it reacted with its own expansion plans whichever perspective you wanna take, so the US had to make Europe, particularly the West Europe, strong enough to counter the weight from soviets to the east. Basically West Europe was needed as a buffer zone. Think of the US as the Great Britain before the World Wars—Great Britain’s foreign policy back then was simply: continental balancing. When Germany grew too strong relative to France and Russia, GB provided assistance to Russia and France and initiated naval blockade against Germany. When France grew stronger than Germany, GB did harm to France and helped Germany. The US after WWII was essentially in a similar situation like that of the GB hundreds of years ago, except this time on a much grander scale. That’s the essence of the Marshall Plan and other efforts put into redeveloping the West Europe.There was a school of philosophy within the government that communist countries, with an explicitly stated goal of exporting communism elsewhere and worldwide, needs to be counteracted. Wherever there’s space not occupied by communism, that space would eventually fall to communism due to the innate expansion nature of communists. Therefore, it’s better to occupy those free space with capitalism and democracy before the advent of communism at those places such as Asia, Middle East, and Africa. This was proven costly and false in practice, as lessons learned from the Vietnam War, secret regime change operations in Africa and Asia, and etc. It turned out that it took so much more money and energy than estimated to practice such a school of thought, and those free spaces were actually quagmires for the US—they were also quagmires for the Soviets like the Afghanistan, nicknamed the grave for empires. So in the end, it was a better idea for communism to spread, and then wait until it fell while in the meantime having CIAs and etc. undermining it till the eventual downfall of commies regimes and the establishing of pro-West pro-US regimes taking place.These are the two reason coming right out of my head for now. Hope it helps, and I will update if I remember anything new.