Packet video transport over networks is expected to experience packet losses due to congestion, link failures and timeouts. Packet-level FEC is often proposed to combat these packet losses and thus improve received video quality. However, the redundant packets associated with the FEC coding will increase the effective network load and, as a result, further exacerbate the network packet-loss rates. In this work, we propose a model framework to describe FEC-protected packet video network transport systems and analytically investigate the overall efficacy of packet-level FEC in improving the end-to-end video quality. We consider a simplified network scenario, where the network congestion performance can be described in terms of a single bottleneck node, modeled as a multiplexer. Our results show that packet-level FEC can significantly improve the end-to-end video quality provided that the coding block size is large enough and the coding rate is appropriately chosen, assuming other system parameters are likewise appropriately chosen. We also demonstrate that, when multiple sources share the multiplexer, FEC coding can achieve significant multiplexing gain in terms of the number of video sources that can be supported for a given end-to-end performance.