The problem is, overtaking is one thing when you got two parallel rails and ample point switches. But when you don't have them or only every 100km or whatnot,

The problem is, overtaking is one thing when you got two parallel rails and ample point switches. But when you don't have them or only every 100km or whatnot, or any of the potential places (such as in a train station) just isn't long enough to accept and buffer a 3 miles long train... then good luck, there just is no physical opportunity for the faster passenger train to speed ahead, not to mention the absurd amount of energy wasted in braking and then re-accelerating that 3 mile freight monster. Fixing this would be possible - either by limiting the maximum length of a train or by forcing the extension of parallel rail segments. The former makes logistics significantly more challenging plus it requires more staff (which is the real problem, long haul isn't wanted much these days, neither rail nor road), the latter is darn expensive and someone has to foot the bill - Congress certainly won't.