He's still limited in what he can do by a fairly clear written document that is extremely difficult to change. Also at least a fairly impartial supreme court to interpret it and the states can challenge executive orders in the courts. There are at least term limits too so you know he will go eventually.
Not so of the UK parliament and PM. The PM could be in office forever, or death at least. With a big majority and the Parliament act the government can do pretty much anything. Nothing to stop them except the the Monarch. People brush off Tyranny, but they shouldn't, very easy to forget history. Fairly terrifying to be honest.
When the revolutionaries broke away in 1776 they did a really good job of setting the US political system up from scratch and learning from the issues in the UK.
The only thing I slightly prefer in the UK system is that it's harder for the PM to launch nukes
. My understanding in the US is that Trump can pretty much just give the order without congress even declaring war. I guess in the cold war that is a pretty effective deterrent but it is also a lot of power invested in one person.