What significance do separation of powers, limited government, and checks and balances have in our American democracy

Separation of Powers in the United States is associated with the Checks and Balances system. The Checks and Balances system provides each branch of government with individual powers to check the other branches and prevent any one branch from becoming too powerful.

the border between arizona and new mexico is a thin, black line; this indicates a state boundary.

its correct: it's a thin line, and it's a state boundary, correct