The U.S could technically do a lot to change the electoral system without constitutional amendments.
For example, we could adopt a mixed-member proportional system for the House of Representatives through simple legislation. We used to have many states use block voting in the past, which was banned by simple legislation, because it was used to deprive black people of representation, for example.
One electoral college problem could be resolved by simple legislation that increases the size of the House of Representatives, making each state have a much more proportional share of EC votes since count of EC votes is their share of Senators + Representatives in the house. Then you'll very rarely have a situation of popular vote lost, EC vote win.
The reason why these don't happen has more to do with the individuals in the major parties not wanting to disrupt their own power-centers, and weaken their party's relative power-share by introducing a multi-party system, as well as just institutional conservativism in both parties.
