From a European viewpoint the Marshal plan was the most important US foreign policy decision in the 20th centaury, including the decision to fight the Germans directly (the USSR would of eventually beat them anyway).
If there was no Marshal plan Europe would have detiriated into 3rd world back water. The Marshal was essential to the recovery of Western Europe, no German economic miracle would of occurred and probably no EU. The USSR would have not felt any pressure to try and engage in a positive manner in Eastern and Central Europe which would also stagnate.
OH and as a very large chunk of the Marshal Plan ended up buying American Goods and Services Economic growth in the USA would not have been as high reducing prosperity
With the Marshall Plan, the US pumped capital into Europe, building European economies. Whereas the USSR sucked capital OUT of their satellites. The end result was that e.g. West Germany was FAR richer than East Germany. That's true. What's not often noticed by westerners is that East Germany and Czechoslovakia were the hi-tech centers of the Soviet Empire. Sure they lagged behind the West, but they had much better electronics, optics, machinery, etc.
That's even with stuff stolen after WWII, and a long experience of 'trading' with the USSR on terms that amount to stealing. If Western Europe hadn't had the Marshall Plan, yes, they'd be a lot poorer for at least the 50's and 60's, but they'd still have capitalist economies and access to world markets, and would be MUCH better off than the 2nd world Soviet satellites. No way, no how would they be 3rd world level.
Heck, they might be essentially as rich today as OTL.
As for no EU, if the west Europeans are on their own, they might be MORE likely to pull together and form a union.