Mainland China was back then completely isolated from the world.
Once Mainland China decided to start trading and opening to the world they pushed as a condition that in order to do so, the US must stop recognizing Taiwan as the legitimate China. And because China represents such a huge trading partner this was incredibly accepted.
We must stand up against the bullies.
The phone call that Trump made with Taiwan's president and his views that the US should revisit the "One China" policy is probably the only good thing he did so far.
Will it continue with Hong Kong or eventually Taiwan?