> The problem is you can vote people out. But the same two parties remain.
Calling them "the same parties" is close to hiding the ball. Those parties have shifted and diverged in multiple directions over their history. See the Civil Rights era for an obvious one--or the rapid separation of both current parties, today. The generally-socdem push of the left wing of the Democratic Party is working to change policy and position. (The reactionary push of the right wing of the Republican Party is working even more dramatically.)
> Which presidents wanted to be dictators? If someone wanted to be a dictator, they wouldn't run to be president in the first place.
This doesn't make any sense at all. Why would they not run? Plenty of authoritarians all over the world and throughout history have come to power through democratic means!
As for "which President", Donald Trump comes to mind for very obvious reasons around attempting to retain power through extralegal means. Whether he has the functioning cognitive capacity to understand what a dictatorship is an open question, but it does not change that he attempted to retain executive control via force and fiat.
The problem is you can vote people out. But the same two parties remain.
> Think of any authoritarian country, and how much the people would love to get rid of some arsehole at the top.
'Authoritarian' countries exist because most of the people support it. And when most of the people are against it, authoritarian countries change.
> The US has managed to vote out presidents that have wanted to become dictators!
Which presidents wanted to be dictators? If someone wanted to be a dictator, they wouldn't run to be president in the first place.