Since you have been asking questions about multinational corporations and being assigned to work overseas, I will answer this in that context.
There are two aspects to culture shock in this context. First, the employee is going to have to deal with culture shock in their everyday, non-working life. When the employee gets to the new country, they will have to learn how to navigate a strange society. They may feel out of place. This can weigh them down psychologically and, potentially, reduce their productivity. Firms may want to have programs in place to “show the ropes” to employees who are new to a country so that they can get acclimated quickly.
Second, the expatriate employee may well have to deal with a different culture within the company. Corporate culture in the foreign country may be different. The expatriate will have to learn how to deal with subordinates in the new culture. This can make it very difficult at first. The expatriate will sometimes be at a loss because they will have to learn new ways to do a job that they have been doing for years. This might be alleviated to some degree by training before the employee is sent to the foreign country, but some of it simply has to be experienced.
When the employee returns home, the same processes can happen all over again as the employee struggles to get used to life in the US. This is known as reverse culture shock. It may be important to give the employee some time to get used to American life before they go back to work so that they are not struggling with both kinds of culture shock at once.