Journey to Babel also seems to play into the UN type model, where the Federation is a union of sovereign worlds, hinting that admission of new members requires a vote from existing member governments.
Some general thoughts on the merits of the US political system:
The US is a democracy in a general sense, technically a Democratic Republic.
If the US is seen as a model for the Federation, then it fits that each world would be analagous to a state, with it's own sovereignty, but signed up to the "Union", with a limited central government for regulating commerce, treaties and mutual defense.
RE: The Electoral College.
This to me is a counterbalance, as a way of preventing pure democracy turning into mob rule.
From having 2 houses in Congress, the 3 branches of Government with distinct duties and relationships, and the limitation of federal and state powers, it seems the US was built on the principal of avoiding a single point of power, such as a King.
Term limits are also an extension of this.
It is also heavily invested in checks and balances, where nobody can generally do anything drastic against the wishes of other branches of government.
This is a good thing, IMHO.
Any goverment system is imperfect. The American system is the least imperfect, and best system human beings have managed to create so far.
Two of the main forms of democracy in use the world today the Westminster (British) or Presidential (US) have their pros and cons.
It doesn't mean that one is better than the other.
I'd agree with that, though I view them as subtle variants on the same basic system.
House of Commons and House of Lords = House and Senate.
President = Prime Minister.
Semantics and some finer points are really the only functional differences. At least on the Federal level.