In the USA, electrical and electronic products must comply with American mandatory laws and regulations, formulated and supervised by OSHA, implement by NRTL. (The NRTL program is defined in the United States Federal Regulations, specifically Title 29 of the Code of Federal Regulations (CFR) Part 1910.)
In the American market, civil or industrial use of the products must pass NRTL (National Recognized Testing Laboratory) testing before being sold in the market. You may see the list of NRTL institutions on OSHA official website: http://www.osha.gov/dts/otpca/nrtl/index.html
If your products have been tested and certified by the testing and certification bodies in the list on the website above, they can be sold in the USA.
UL lab: UL test report and UL certificate
V-TRUST has established long term and cooperative relationship with UL, and you can apply the certification service from V-TRUST directly.