Control as in day to day operations. Who organizes visiting vehicle ops, consumables, etc.
Those Russian engines are only used occasionally. Mostly, Station relies on US-side control moment gyros for attitude control. Also, the huge solar arrays (USOS, again) act as controllable aerosurfaces. In a pinch, you could actually use the solar arrays alone for desaturating the gyros. Until Shuttle retirement in 2012, Shuttle was also used for reboosting Station. It's possible for other visiting vehicles (ATV, HTV, Cygnus, Dragon, Proton, Soyuz, Starliner, Dream Chaser) to reboost as well. Mostly Proton does the reboosting, but that's just an operational decision.
Something like 75-80% of the mass of Station is USOS. Something like 80-90% of the power as well. Zarya, a Russian-built module that was the first part of ISS and which contains propulsion systems (Ukrainian-developed control systems), was actually bought and is owned by the US.