Honestly unless the people in here defend abolishing the states and ruling all of the US as a single unitary state like say France, they should defend the existence of the Senate.
One of the biggest aspects of federalism is the existance of a second chamber, that is represented in a 1 state = 1 vote basis, to counteract the lower chamber that is 1 person = 1 vote (at least in theory).
Since I am a big fan of federal states for the most part, and there is no real reason to turn the US into a unitary state, I would keep the current senate structure for the most part.
As for in terms of legality, while the Senate can't be abolished it could still be rendered powerless by making it into a chamber that does not matter and can be overridden by the House like the British House of Lords (or the Spanish Senate for that matter).
That doesn't make sense. If the Senate is "rendered powerless" it can't "counteract" the House.
Not necessarily, the House of Lords is - in tack50's words - "powerless," but it does still counteract the Commons as a revising chamber: scrutinizing legislation (they can hold a bill for up to a year), examining if legislation is workable &, if not, make suggestions & send legislation back to the Commons to be re-worked. They do a very good job of making a load of small changes to legislation & very, very occasionally, will block a piece of legislation from going through: generally speaking, they can only do this temporarily & not outright, but if they time it right & do it for the right reasons (as they usually do), it can have a major impact & be an embarrassment for the ruling party in the Commons.
