Actually I believe the first strake mod was on the Westland Sea King during the Falklands Conflict in 1982when the Mk 4 Commando version was rush-fitted with them.Subsequently all the Sea King fleet had strakes fitted and the idea was also the idea was adopted for the new build EH101 and more recently the A109 and AW139 .The introduction of strakes on US aircraft post dates these earlier examples.
Whether NASA did the original work I don't know but it did patent thr design in the US and Boundary Layer Research won the civil sales agreement .Vis-a-vis Bell My belief is that the company is just covering its back.