MMA was never going to get sanctioned in the US if it still had soccer kicks.
Hell, we still had knees to the head of a grounded opponent when NJ, one major Athletic Commissions in the country, started to sanction MMA. If it wasn't Gan McGee kneeing an overmatched Brad Gabriel's head into oblivion while he was on the ground at that IFC event in Atlantic City (that I attended by the way), we might still have knees on the ground in MMA in the US. NJSAC chairman Larry Hazzard took one look at that and said "NOPE" and drafted the Unified Rules of MMA (basis for all of MMA rules in the country even up to this day) which banned knees to the head of a downed opponent.
Now that's not to say some Athletic commission could draft their own rules and allow knees on the ground, or hell even soccer kicks to the head (wasn't there some promotion in Alaska that tried it?), but it's unlikely that if some promotion tried those rules that they would be allow to hold an event in one of the major commissions. Kind of a revenge thing for going against their rules so to speak.
Hell, when PRIDE held their events in Las Vegas, they had to alter their rules to disallow kicks and knees on the ground, even though that's not their rules.
As far as Zuffa's then plans for PRIDE when they bought them. According to Zuffa back then, they wanted to keep PRIDE running and still hold events in Japan. Even go so far as to keep PRIDE champs as is and defend titles, then at the end of each year have PRIDE champs battle UFC champs for a Superbowl of MMA of sorts.
There were a bunch of problems though. The one that Zuffa kept bringing up was the sad financial affairs of PRIDE that they inherited with the purchase that they eventually unable to untangle. Apparently their debts were too much to overcome. Then they couldn't get a TV deal in Japan. The dirt of the yakuza scandal apparently wouldn't wash off for any TV station to air PRIDE again.
Lastly for a more cultural angle, you don't get too far having foreign ownership of Japanese companies in Japan. It's matter of PRIDE to the Japanese people (pun intended.)
So Zuffa running PRIDE events in Japan was pretty much basically doomed from the start. Couple that with ALL combat sports losing interest from the Japanese public (with K-1 falling soon after, and DREAM and Sengoku not surviving after that), really no way for Zuffa-PRIDE to go anyway in the Land of the Rising Sun.