The car structure has not changed, I think they raised the bar on the crash test...
No, NHTSA's crash test has not changed since 1990. Earlier 5-Star Safety Ratings provide front crash, side crash, and rollover resistance ratings from 1990 - 2010. New 5-Star Safety Ratings feature an Overall Rating Score to make it easy to compare newer vehicles from 2011 and newer.
It's Mazda who changed something which affected NHTSA frontal crash test on passenger dramatically:
2015 Mazda CX-5 gets 5 stars on overall rating, and 5 stars on frontal crash with 5 stars on driver and passenger.
2016 Mazda CX-5 gets 4 stars on overall rating, and 4 stars on frontal crash with 5 stars on driver and 3 stars on passenger.
The others:
2016 Honda CR-V gets 5 stars on overall rating, and 5 stars on frontal crash with 5 stars on driver and passenger.
2016 Hyundai Tucson gets 5 stars on overall rating, and 5 stars on frontal crash with 5 stars on driver and passenger.
2016 Subaru Forester gets 5 stars on overall rating, and 4 stars on frontal crash with 5 stars on driver and 4 stars on passenger.
2016 Toyota RAV4 gets 5 stars on overall rating, and 4 stars on frontal crash with 4 stars on driver and passenger.
2016 Chevrolet Equinox gets 4 stars on overall rating, and 4 stars on frontal crash with 5 stars on driver and 4 stars on passenger.
2016 Ford Escape gets 4 stars on overall rating, and 4 stars on frontal crash with 4 stars on driver and passenger.
2016 Nissan Rogue gets 4 stars on overall rating, and 4 stars on frontal crash with 4 stars on driver and 3 stars on passenger.