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In general though, our interests have been served by usually sensible use of American power - so a weaker, isolationist USA, I don't think will be in our interest at all.
I think it is from the view of Europe in the long term. Europe emerged from WW2 pretty much broken, requiring a huge effort plus extensive loans from the USA to rebuild, not just the bombed out buildings, but also a tattered economy. We could see then that both superpowers, USA and USSR, were and still are a menace for world peace but because they were engaged in a cold war so perhaps they would leave us alone to get on with what we have had to do. Since the USSR was disbanded, China gradually joins the previous two super powers. The USA declines, Putin's Russia rises on the back of energy and metals exports, China of industrial manufacturing. Russia was no longer perceived as a cleat and present threat, the world goes through a short period of peace until the CIA under Bush found new enemies in oil rich Middle East. Now the USA have run out of enemies in the Middle East, their attention turned back to Russia.
One predictable thing about Trump is because he can't even think beyond the end of the day leave alone the end of the week or end of the month. He can't do anything long term. He'll leave Ukraine to Europe which suits Europe fine. Europe needs time to rebuild its military while trying to remove its dependency on imported fossil fuels. I think Putin will start negotiating before the end of the year because he knows he can't match the industrial power of the EU, Germany alone can outspend him. Germany needs the war to continue if it opts to have its own nukes.