Hi Customer (name blocked for privacy),
The main reason is that it is easier to set up business in some other countries. The US has certain guidelines that many firms are unable to either live up to or are unable to meet in the first place. With the advent of an increased awareness regarding terrorist activities, the US has revised a lot of their homeland security and business laws that make it harder for certain companies to set up office there. In addition the levels of bureaucracy in the US is a turn-off for many firms and so they opt to open their offices elsewhere.
More help available if needed.
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