Federalism and the 10th amendment work together--the 10th Amendment states that if something is not covered by the Constitution and there is no specific federal power, then the power goes to the state.
Federalism is the principle that government should be divided between a central power and regional powers. In the case of the 10th Amendment, if the central power doesn't have explicit power to do something then the states have the power to do so.
After the end of World War I European countries were in decline, their industrial and agricultural sectors suffered a reduction of more than 30%, causing a very strong impact on the economy and thus forcing these countries to look for loans and to import products from another country. In this context of poverty, European countries needed to buy many products and borrow money, in this moment, the United States of America enters as the nation that can meet European needs; at high interest rates, of course. The US had its territory spared during the war and had a large number of exports and loans of money to Europe, causing its economy to be boosted and its national income doubled.
Checks and balances work protect us from the govt getting more powerful than the other