A lot of the aspects of American law that are viewed as non-democratic were put in place specifically because of the balance between the power of the central US government vs. the governments of the individual member states.
Something most Americans, let alone non-Americans, don't understand is that the Federal government was a creation of the member states, not vice versa. Perhaps the best example of this aspect driving what currently appears to be non-democratic traits is the composition of the US Senate.
Every single member state, no matter how big or large its population, gets 2 senators. Most American voters (it happens to be left of center voters right now, but if it favored left-wing candidates, right of center voters would flip out) feel like this is unfair, and question why it was put in place.
The reasons hearken back to the creation of the Federal government. The individual states that had to cede their own power for a federal government refused to join the union unless the Senate was created, with equal representation for all member states, regardless of population. Connecticut, Delaware, New Jersey, and other states which are now ironically all left leaning politically, were concerned that the states with large populations, such as Virginia and Pennsylvania, would obliterate the concerns of their citizens in a purely democratic system. Hence the Senate, and as a side-effect, the electoral college system. Think of them as a geographic weighting, where each member state's power by population is limited or expanded to create a more balanced power structure.
Regarding the "USA has subverted democracies in its sphere of influence", while this has been true with certain nations (Shah in Iran, Saudi, Guatamala, etc) it has also not been the case with others, such as all of Western Europe post WW2. Nations liberated by the Soviets weren't actually allowed to dictate their own futures, unlike those liberated by the US.