In order to obtain a patent in the U.S., the invention must be original, meaning that you must be the inventor of the invention. Also, under 35 U.S.C. 102 (a)(1)
the claimed invention was patented, described in a printed publication, or in public use, on sale, or otherwise available to the public before the effective filing date of the claimed invention.
Since the invention was patented or published in a printed publication in China prior to your filing in the U.S., it is not eligible to be patented in the U.S.
It might be possible to change the design sufficiently so that your improvement is patentable. The changes would have to be sufficient so that the invention is "unobvious" to one skilled in the technology to which it pertains. That is a significant burden, but may be possible. You may also be able to change the design sufficient to obtain a design patent. Whether or not your changes reach those levels are a significantly different question beyond the scope of the present question.
The only other possibility to obtain exclusive rights would be to contact the Chinese patent holder, see if they are pursuing patent protection in the U.S. and obtain an exclusive license from them.
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