It was the Marshal Plan that contributed to a post-war boom in Europe that was not seen after World War I, since the plan injected millions of dollars in the European Economy.
The Marshall Plan was an initiative launched by the US in 1948 to help the recovery of Western European countries after WWII. $ 12 billion were sent to rebuild those countries and to boost their economies by rebuilding factories, infrastructures, civil buildings, etc.
The US had adopted the containment strategy, a foreign affairs approach which focused on stopping the spread of communism worldwide. Therefore, rebuilding Western Europe under the influence of the US was beneficial because the Western European powers would side with the US and act as a barrier for containing communism, that was in fact suceeding on the Eastern regions of the continent.
The 16th Amendment gives Congress the power to collect taxes from incomes. Congress uses these taxes to build roads, manage construction, maintain public resources such as libraries, and keep an army.
To look at it purely from ideological view, communism is the total opposite of capitalism. They thought that communism was an extremely dangerous ideology.
