There is a significant difference: Trump is term-limited, and Putin is not.

That doesn't make the US more reliable. It may well make it less reliable. Putin cannot live forever, but Trumpism can. What makes America unreliable isn't one politician, or even a cabal of politicians, but a large section of the electorate who wants exactly what Trump is giving them. They will continue to vote for that even if he dies.

Even if his opponents take over, it will only be temporary. Trump's constituents will always be seeking to win the next election. And since the American system is designed to prevent a President from taking absolute control, it's practically impossible for Trump's opponents to make deals that can be relied upon.