the blackjack i believe was meant as a soviet counter to the lancer, so design criteria like variable wing geometry could be "inspired" from the b-1. then again the tupolev design was chosen by the soviets by '73, which i believe was before the b-1's first flight.
There is certainly a possibility of industrial espionage involved in the design of the blackjack, but imo if that is the case, it's probably a bit further in the past than the b-1 project. the tu-160 was somewhat based on tupolevs civilian tu-144, which is rumored to be (at least partially) a product of espionage against the french concorde designers. Espionage, that if true, was effective to such a degree that tupolevs design flew before the concorde did.
Mig-3. not the best performing fighter of ww2 perhaps, but it makes up by looking damn awesome. looking awesome wins the war, right?