First of all: who has been awarded custody?
If she has been awarded custody then under American law you would have certain "visitation" rights which include also the right to keep in contact with the children by phone or mail or other means.
But this of course is American law. While your ex-wife would be bound by this in America, American courts have no jurisdiction in Taiwan. So you would have to find out what Taiwanese law says to this.
There are many countries in the world which have similar provisions in their law and, what is more important, which honor a foreign court decision in regards to this.
So there are these possibilities:
You have to find out what Taiwanese law says about this.
If Taiwanese law gives a parent who does not have legal custody contact and visitation rights, then you would have to find out if you need a court order of a Taiwanese court or if Taiwan would honor and enforce the American court order.
You would want to find a lawyer who is familiar with Taiwanese family law to pursue this.
