Places like the US and UK need to change their system, but politicians have an incentive not to change anything.

Fortunately with the US, its decentralized system allows experimentation at the state and local level. My city (Portland, OR) just switched to ranked choice voting for city council along with a host of other changes. Voters statewide will soon be able to vote on using RCV for state races. Meanwhile, ranked choice has been implemented in several other states and localities across the country. It will take a while, but I think ranked choice will become the norm within a few decades.