Under the Visa Waiver Program (VWP), nationals of certain countries (South Korea, Canada, UK among others) can enter the United States without a visa. Generally, those admitted under the VWP cannot change or adjust status under INA 245A. However, there is an exception for immediate relative.
Definition of Immediate Relative under the INA:
Immediate Relative means spouses, children (under 21 of age and unmarried) of U.S citizens (USC).
VWP and Immediate Relative Exception:
An individual admitted under VWP can stay in the United States for 90 days (usually.) Immediate relative can seek to adjust within the 90 day window.
There are local USCIS offices that have taken much more generous approach. Depends on the location, the local USCIS may adjust the VWP immediate relative’s adjustment of status even after the 90 days window. However, this guideline/exception is informal and may be changed in future. Please consult with a local immigration attorney.
THEREFORE, please consult with a local immigration attorney if you wish to adjust your status. There may be local rules/customs that you should be aware.