There are a number of carriers which offer "courtesy" 24-hour cancellations. But, that has nothing to do with either US carriers or non-US carriers on tickets to or from the US. They are covered by the 24-hour cancellation rule, e.g. law.

Interestingly, all three legacy US carriers, UA, DL, and AA, provide greater than the Rule requires, both in terms of how the 24 hours is calculated and when it cuts off (the Rule does not require "free" cancellation within 7 days of departure).