Outcomes much more unlikely than that are realistic because they are real.
* U.S. support for Israel after '67
* EU turning on Yugoslavia, ripping a piece of it away and giving it to a group of bands who were previously advised by EU officials how to garner the needed support
* various U-turns in regard to being allied / rivals in the Second World
* Molotov-Ribbentropp pact
* U.S. turning away from preventing/destroying left-leaning governments in Latin America
* half of the U.S. turning towards domestic economic and fiscal policies that hurt their own self-interest
* Germany and others giving up stable national currencies and lender of last resort
* collapse of Apartheid in South Africa
* conservative German government U-turning against nuclear energy
* U.S. so-called "conservatives" u-turning towards nation building '02
* Britain allowing its colonies to go
* U.S. becoming involved in East Asia post-'38 on behalf of China (post-Nanking) despite this actually harming its trade interests
* U.S. participating in WWI without serving any of its interests, after a three-year propaganda campaign by Britain
* sudden U.S. tolerance of North Korea as a nuclear power
* Turkey turning away from EU towards its own neighbourhood policy
* France dropping Arab dictators in favour of good relations with Arab populaces
* Saudi Arabia's sudden tolerance for foreign troops '91 and later
Such U-turns happen all the time, just look at history.
China has even turned on former allies before, and that didn't take any outside influence.