In this letter, we investigate the ergodic performance of rate-splitting multiple access (RSMA) with finite blocklength (FBL) in high mobility communication systems to meet the ultra-reliable and low-latency (URLLC) requirements. Considering the imperfect channel state information at the transmitter (CSIT) originating from the high mobility of vehicles and the time delay of channel feedback, we analyze the statistical properties of signal-to-interference-plus-noise ratios (SINRs) for common and private streams at the desired vehicle. Next, we derive the closed-form expression for the ergodic sum-rate in FBL RSMA systems considering an arbitrary number of transmit antennas, number of vehicles, vehicle speeds, blocklengths, and block error rates (BLERs). Compared to other benchmarks, such as FBL non-orthogonal multiple access (NOMA) and space division multiple access (SDMA), the proposed scheme holds its optimum performance to meet the stringent BLER requirement while maintaining a prominent reduction in blocklength.