2 Amendments draatically changed the role of the Federal Government
16th (1913): Authorized federal income tax.
17th (1913): Established direct election of U.S. Senators.
The 16th Amendment granted Congress the constitutional authority to levy a federal income tax without apportioning it among the states or basing it on the U.S. Census. Previously the US Government could only collect taxes directly from tariffs, OR by taxing the states based on their electoral votes. Now the Government could raise money without ANY input from the states.
The 17th Amendment, established the direct election of U.S. Senators by popular vote, replacing the original Constitutional provision where senators were chosen by state legislatures. This eliminated the Main reason for the US Senate. The Senators were elected solely by the State legislators, therefore beholden to the states. The Senate was intended to be a body representing the STATES.
These two amendments eliminated most state oversight of the federal government. They led to the huge federal government we see today.