State reps have a much more informed and salient interest in maintaining their state’s sovereignty, as their power directly derives from it. Much of what the fœderal government does now to usurp state power is to simply bribe the states to change their policies (e.g. the drinking age, but many such examples). Would state reps willingly select senators who would bribe them to change their own policies?

> State reps have a much more informed and salient interest in maintaining their state’s sovereignty,

Bullshit.

The smaller the democratic unit, the more likely it is to be unduly influenced by local power and wealth. State reps are far more likely to represent the interests of the local power and wealth than they are "their state" (by which I mean "the people of their state")

> Huh? Previously, state representatives elected senators; after the 17th, the voters did. How does either of these things end "state representation" ?

Who’s their boss? At the moment senators answer to the people of a state, previously they answered to state government.

This changes the reasoning of why we have laws at the federal level. The senators representing a state would be fired for giving up sovereignty; not so for those elected via popular vote. Those elected by popular vote are incentivized to give out goodies to the masses.

State legislators could easily fire and switch senators. Public opinion on the senators didn’t matter nearly as much. If a person of a state wanted influence over the senators they had to focus on local elections.

There’s a whole lot of changes, not really sure what’s being missed?