The US had reclaimed land from ISIS before Russia ever got involved in Syria. The problem is that ISIS puts itself among the general population, so bombing is of limited utility unless you want to hurt civilians. Bombing is limited utility unless you have a ground force also, and so far Obama was trying to find a ground partner to work with. Remember, Obama was the guy in Washington way back when who didn't
want to go into Iraq in the first place.
ISIS took all this territory when Obama honored the agreement to withdraw US troops from Iraq, in fact the Iraq government was pushing us out. A couple of years later, ISIS started crumbling the sham Iraqi army built under Bush. 600 Iraqi fighters took over the city of Mosul, which was "defended" by thirty thousand
Iraqi forces. Apparently, under Bush's nation-building program, the Iraqi forces were taught that the proper way to defend a city is to turn your rifle over to the invader and then invite him over to dinner next week.
Nevertheless, some territory had been reclaimed from ISIS. To say we were not fighting ISIS is just inaccurate, and I don't see any ISIS factions surrendering to the Russians either.