What developments caused the percentage of Americans who voted to plunge after 1900, and what role did courts play in anti-democratic developments?

The developments that plunged the percentage of American voters after 1900 are:

The Seventh Amendment Exclusion of Immigrants African American Voters.

The role played by courts was hostile.

Explanation:

The Seventh Amendment is a part of the Constitution of the United States that gives the right to a jury trial for certain civil cases. The amendment was added to the constitution by Thomas Jefferson on 1st March 1792.

Immigration and Naturalization Act of 1952 was the act that codifies the immigration to the citizenship of the United States.

The Fourteenth Amendment of the Constitution of the United States gave rights to African Americans to vote. Though this amendment still did not give full rights to the African Slaves to vote, so the government passed the fifteenth Amendment also.

The above developments was the cause of plunged percentage in American votes after 1900.

The role that courts of America played in the development of such anti-democratic reforms was hostile. It did not interfere much in such developments.