Federalism has been slowly eroded over time, in the U.S., the most prominent a Wilsonian-progressive, 17th Amendment. I've previously written in great length as to why popularly elected Senators was a negative, but to name just a few:
1) The House was meant to remain the only unstable chamber within the Congress, subject to the public tenacity district by district and localizing politics, leaving the Senate stable and apolitical, thereby preserving the sovereignty of various constitutional mechanics the Senate provides for. Take the Judiciary, the politicization of the Kavanaugh appointment, while examining all previous appointments over the past century, since the Amendment was ratified. They're mostly progressive, populist, and willing to stand for the Federal government's violation of property rights and expansion, among other key issues, such as allowing for unions to conduct racketeering, blackmail, and economic terrorism, for example;
2) The 17th Amendment made it easy for wealthy coastal areas, of greatest economic scale, to influence and dictate Senate elections to the rest of the rest of the country. Without a 17th Amendment, any influence must be made at the local, district-level House as that's the constituency they're held to account, while they were the ones to appoint Senators. It's also more difficult for, what has become a Corporate State, to dictate the elections of 435, 2-year term House seats, than it is to dictate the 100, 6-year term Senate seats. Local interests in New York or Florida shouldn't dictate the elections of 25 fly-over States. This is why minimum wage and other labor laws, for example, have been accepted by a Senate, at the cost of economic development for the inner-country majority, while all economic interests are saturated around economies of scale (economic fascism), burdening the rest of the country with market-entry barriers and various other forms of regulation that have regulated out various free-market processes within many
