It looks like the Korean application never became a patent and the WO number is for the PCT application. PCT applications need to enter the national stage in one or more countries to actually become a patent. I do not see that this ever entered the U.S. national stage
Patents are territorial. Other than some odd cases, they only constrain actions within the country that issued the patent. There are some small exceptions like things at sea.
However there may be patents other than this that cover what you plan to do. Just because there is not a corresponding U.S. patent there may be other patents by other inventors or the same inventor that could cause a problem.
One way to start looking is to look, on google patents for example, at previous work cited in the patent application at later work that google patents links to. These are things that the application cites. On google patents there is also a link to "similar documents".
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GB2381183A * 2001-10-27 2003-04-30 Peter Lawton Jewellery for pierced navels
WO2007142416A1 * 2006-06-05 2007-12-13 Seung Hoon Lee Headgear capable of being attached and separated ornaments