1. America has a very strong republican (small “r”) tradition. Most people get annoyed when children of leaders try to base a career on their parent’s success.
2. Most monarchies tend to flop except for ones such as Britain in which they steadily gave up power and ended up as being apolitical and powerless (which in itself is useful, since in the US there is no one who is able to be apolitical).
3. Trump has managed to alienated at least half of the country. A successful president would have something like 80% approval ratings at least. Few presidents approached that (Washington probably but he was unique, Lincoln by the summer of 1865, Franklin Roosevelt by the fall of 1945, you get the picture).