There are several things that might be done, short of blowing them out of the water, the preferred choice. Several of these alternatives would also be entertaining for the US ships’ crew.
For example, it should be easy to set up an Active Denial System dish on board, with minimal effort. This is the one that makes skin feel like it is burning. It is effective up to 500 yards.
Second, many US vessels have radar powerful enough to smoke and most likely blow up any electronic gear aboard their boat, just by pointing it at them.
But I’m sure that the USN has invested lots of time, effort, energy and money into make the efforts of Iranian speedboaters futile.