Jamming isn't destructive interference, which would require knowledge of the exact signal being sent as well as the exact location of the transmitter and receiv

Jamming isn't destructive interference, which would require knowledge of the exact signal being sent as well as the exact location of the transmitter and receiver. Jamming is overwhelming the receiver with a stronger signal in the same frequency band so the weaker one cannot be received. Think someone screaming over someone else whispering. Phased array beamforming absolutely helps make jamming more difficult. Jamming is all about reducing the signal to noise ratio in the channel until it is unusable. Directional antennas (of which phased arrays are electronically steerable versions) have more gain in the direction of the desired signal and less towards unwanted signals located in another direction.