ASC842-VARIABLE RENTS

Dear Experts,

Under ASC842, Variable rents linked to Indexes are to be capitalised into ROU,Liability upfront to the extent they are known.
Any subsequent changes to these rents are to be expensed off unlike IFRS16, where they have to be considered into remeasurement.

My question is that to expense it or capitalise, is that an elective? Can USGAAP customers capitalise and remeasure Liability and ROU like IFRS16 or is it mandatory to 'Expense' if off only?