Since Power Rangers came first so I kind of thought that it's time to see what Super Sentai contributed to Power Rangers. Here are some I can think of:
The idea of racial diversity. Well Super Sentai doesn't have it due to language barriers I assume but I think Battle Fever J may have inspired the idea.
The idea of teenagers fighting evil was from Turboranger. I kind of thought that MMPR had some common elements with Turborangers aside from just fighting evil, the school environment, pressure and more. I even think Dr. Dazai may have inspired making Professor Phenomenus. In fact I felt like a lot of PR characters give Pre-PR Sentai nostalgia.
The additional ranger becomes a replacement leader. This was kind of from JAKQ with Big One. I ended up comparing Tommy to Big One for this reason. :-P
The creation of bad-ass female characters. Well for some reason, Saban replaced the male with female counterparts in my own assumption due to cultural differences. For one, Trini Kwan's being peace-loving yet a skilled martial artist reminds me of Bioman's Mika Koizumi, Sentai's very first yellow ranger.
The Ohranger vs. Kakuranger special was ported into Power Rangers Zeo. For Sentai, the movie is impossible due to some conflict elements so fans were left to speculate to how it happened since Sentai's canonicity is left to fans' imagination. This allowed writers to make special episodes for Power Rangers while in Super Sentai, they happen out of series and fans were left to decide on whether it was canon or not.
A female commander was later added into Power Rangers, that was with Power Rangers Turbo (arrival of Dimitria who in Carranger may be equivalent to Radiata Fanbelt) and the first human was in Gingaman as Commander Renier and a much younger one in Lightspeed Rescue's Angela Fairweather.
Power Rangers' Contribution to Super Sentai