[Bruno]

As a non-American I'm not an expert, but both their houses are geographically based - but they're based on different geographical boundaries. I believe.

The Canadian parlimentary system was set up somewhat along these lines, with the House of Commons being geographical, and the Senators being appointed for life by the current Prime Minister (although with traditional emphasis on equal geographic representation in the Senate). This results in the Senate having a bias to the previous PMs party at the beginning of a new government, and a bias to the current PMs party after a few terms.

But now the House of Commons is geographic but dominated by party lines, and our Senate is losing party affiliations; no organizational structures survives centuries without change.