The US has burned trust well past 4 years. This has shown how the US political system enables this. Every 4 years they elect someone who has the power to just toss out everything the previous administration did or committed to. Every 4 years... and the US is so politically divided that it only takes a few percent of opinion change at each election to swing to the other party with polar opposite views. As a result, why would any other country now trust the US in any agreement? (not to mention the large number of agreements they have signed then just abandoned later) Four years is nothing time wise.. barely enough time to get an agreement fully implimented before the US can just say "Nah..." There will be significantly less trust for the US even beyond the Trump era.