How does lack of Marshal Plan affect US economy, considering European economies are going to be a lot weaker without it
From my reading the worry was that surplus production in the USA needed an outlet and European reconstruction was a handy one. It could also be sold to the US public and tax-payers as an insurance policy to keep Western Europe from going communist. After that, Cold War military Keynesianism served to soak-up US productivity.
But other writers have argued that US productive capacity could have been absorbed by higher wages for US-American workers and that Europe could have rebuilt itself without Marshall Plan dollars, albeit more slowly.
So, in this timeline, without the need to save Europe from Communism, there is less US-financed reconstruction and this smaller amount is spread across Europe into the Soviet Union, resulting in slower economic development there and in Japan.
Higher wages for North American workers is delivered in such a fashion to make conservative trade unions see the benefits of US capitalism (Europe has far more socialism).
The absence of high-levels of Cold War tensions (until the 1960s) reduces the call for massive military spending, which likewise gets directed into higher wages.