A few big states and numerous small ones is all one needs to control the US Senate, which the Republican party seems set to do for the foreseeable future. Furthermore, the GOP controls most governorships and state legislatures. The latter has allowed them to gerrymander to the tune of ridiculously lopsided majorities in state house caucuses and federal congressional delegations - which means they will be allowed to continue gerrymandering every decade unless a state's demographics so warp in ten years that Democrats get lucky, or we manage to pass federal laws reforming the process. Such reform will likely be impossible due to the Senate imbalance - and the fact that it would still have to withstand a 6-3 conservative majority on the Supreme Court.