How can ethnocentrism have an impact on the success of an international manager?

Ethnocentrism
would have a very negative impact on the success of an international manager.  Ethnocentrism is
the general belief that your own ethnic group is better than other groups.  An international
manager would be badly hurt by this belief because they would tend to look down to some extent
on people from other cultures or ethnic groups.  They would have a hard time getting along with
such people because their attitudes would probably end up being communicated in one way or
another.  They would have a hard time accepting feedback or taking comments from people of other
ethnicities because they would not really take those people seriously.

In
other words, an ethnocentric international manager would not work at all well with people from
other ethnic groups.  Since an international manager must by definition work with such people,
an ethnocentric manager would not be likely to succeed.