I think it's more accurate to say there weren't many expansionist tyrants whilst the US was looking interested in world policing. The Soviet Union had to be very careful about what they did in Europe despite having their own nuclear umbrella, Saddam could tyrant all he wanted until he annexed a neighbouring state the US felt vaguely positively disposed towards, and whilst you could fight petty border wars or maybe fund a coup against a neighbour somewhere less strategic you didn't have the option of doing what 1939 German and Japan and Russia did or even what 2020s Russia is trying to do and China is probably thinking of.

The US didn't install MBS, he's the prince of a monarchy that predates American involvement by centuries. The same goes for any ruler in Saudi Arabia; we inherited that alliance, we didn't create the House of Saud. Maintaining our relationships with an existing government is not the same as overthrowing a democracy and installing a dictator like what happened in Iran or Chile.

What dictators has the US installed after the Cold War that balance against Saddam, Noriega or the Taliban regime change?

I said installed or propped up. They are certainly propping up the Saudi royal family, increasing their prominence on the world stage, even as they have killed American citizens and are conducting wars in the region. Also, the current Saudi royal family has been ruling at best since 1902, so nowhere close to "centuries" (though they do have ancestry going back to the 1700s to a royal family that briefly controlled a part of modern day Saudi Arabia).

In regards to other dictators, I'm not sure why you're only looking at post-Cold War history. What's most interesting about this period is the amount of failure by the USA to effect regime change, despite very clear evidence of such attempts, both against dictators and for them. We even have the interesting case of Haiti, where the USA supported a coup to get rid of president Aristide in 1994, then they led a UN-approved military action to re-instate him in 1998, then supported another coup to get rid of him in 2004. After the first coup, a military junta was installed, and the USA was one of few countries which traded with them. You also have US support against several islamic populist leaders in various Middle Eastern and North African countries, typically preferring secular military leaders instead - often leading to either protracted civil wars or to brief regimes that couldn't hold power. You also have a series of attempts at regime change in quasi-democratic countries, ostensibly for more democratic leaders, that failed - leaving uncertainty on whether those that they attempted to prop up would have been better or worse; the clearest example of this is the attempt to install Juan Guaido as the President of Venezuela after a deeply controversial vote.