There are multiple ways to end up an authoritarian State. You can add many regulations, then have someone come to power and use those regulations to repress society (a good example would be Germany in 1937), or have a weakening of the institutions protecting citizen's rights, which is something the US is experiencing.
It has started before Trump, I think that a turning point was the Patriot Act, but Democrats didn't overturn it and picked their ennemies, too[0].