“Senators were originally appointed by their respective States, not elected.”
I got that, but how does that “destroy one of the Founders’ initial checks on an excessive federal government by destroying the states’ veto power over the federal government”?
Appointed Senators are not elected, they were appointed to represent the State’s interest only. They were not popularly elected and were not prone to the populist swings of opinion present in the House. The House originated Bills, the State appointed Senators had veto power over them.