About an inch or so of my Rx antenna broke off today leaving only about 3cm of loose antenna hanging out of the ant. tube. Will this cause any range or interference issues? Keep in mind that I still have an entire antenna tube's lengh worth of antenna plus some still working, but I do know that antenna lenght's are different for different channels in the Rx.

Oh, and I sometimes swap out my systems of measurements because I'm used to using all metric in science class...2.5cm = 1 inch.

it will only effect your car if you drive really far away, or if you have like police cars transmitting radio signals around you. the dirt lot field i drive my rc in is next to a new police station and somtimes i get interference. really annoying [:@]

An inch or so should not hurt all that much.
If it were cut off at the base instead of the top, then you could have issues.
A rule of thumb length for am & fm rc radios is 20". Most rx antennas on rc's are within an inch or so of that.
While it's true that antenna length is dictated by the frequency being used, rc systems are designed to operate over a range of channels (or frequencies) without having to retune the transmitter or the reciever. Hence they don't have to be an "exact" length.