From a British viewpoint, in terms of policies, there is no discernible difference between Republicans and Democrats. Both are hard-Right parties in hock to corporate interests.
The major difference between them has been Trump. He is the only candidate for decades on either side who has not been a Party apparatchik or lifelong politician. He poses as a successful businessman/man of the people who rails against politicians and intellectuals and proposes simple solutions to complex problems. In doing so, he has cornered the market on the votes of many ordinary people who seek a Disneyfied version of the world in general and America in particular, and who are afraid of what they see as a wave of change that will sweep away their ideal way of life (the one they dream about, not the one they have).
Universal suffrage is morally and ethically correct, but as with all correct choices, it carries a price and a risk. The price is that it gives a say to people who are neither intelligent nor informed enough to make a rational decision, but who vote with their feelings. The risk is that the emotional vote sometimes goes to someone whose agenda may be anything but moral and ethical.
Hence the closeness of the vote this year. 2020 has not been a good year for cool heads and rational thinking.