The US east of the Mississippi isn't appreciably less densely populated than Europe, and given the general age of the eastern track routes compared to Europe and the topography (Appalachian mountains need a decent amount of tunneling) and likelihood of overpasses (the road network is probably as dense in the US as in Europe), I can't imagine that there is substantially more work needed to adjust the loading gauge in the US for double-stack than it would be for Europe.

Probably the big differences are that a) the US already had a comparatively roomy loading gauge compared to Europe before conversion was necessary and b) the West Coast-to-Midwest routes were probably more likely to be double-stack-compatible before the projects started and provided a seed route to develop the concept before the expensive loading gauge conversions in the east had to take place.

Electrification doesn't affect double-stacked routes other than needing (I think) an extra ~2 ft of height compared to non-electrified track. The cost of relaying catenary cables isn't going to be all that high: electrifying track from scratch in the first place appears to cost about $1 million per km, and a lot of that cost will include the substations which don't need to be replaced; actual costs of replacing the gantries is likely to be less than half that. That's of course assuming that there is actually room above the track to support the new height.

Fair enough about the eastern part, but as you say we're lacking something comparable to the western half as a starting point. I'd been sort of implicitly averaging the two halves together for the US.

Regarding electrification, yes, it's not rocket science, and the cost of raising bridges and tunnel clearances will usually dominate, but because electrification on the main lines covers basically every metre, I'd think that the costs would still add up significantly.

There are overhead electric rail lines supporting double stack freight in the NEC USA, China, India, and possibly elsewhere. There are YouTube videos and images on web. AAR Plate H (20’ 2”) is the North American rail loading gauge for double stack containers, so 21’-23’ for the electrical lines is enough clearance. Nothing unusual here, straight forward for new lines, but as you noted potentially a lot work/cost on existing lines to create enough clearance due to raising overpasses/structures and/or undercutting them and tunnels.

That's tight. Here's a document from Network Rail on the practical problems of trying to increase the loading gauge in the UK so containers can fit on electrified lines.[1] That's just to make room for single height containers. In the UK, the catenary clearance is sometimes reduced to get under historic bridges, but that requires slowing trains way down. Sometimes the rail bed is lowered, but that creates drainage problems. Raising historic masonry bridges is even harder. This document has good pictures of all the problems.

[1] https://www.bathnes.gov.uk/sites/default/files/sitedocuments...

Much of the Eastern Seaboard in the US still has areas that are limited to single-stack container trains. Wikipedia has a list of some of the big remaining ones: https://en.wikipedia.org/wiki/Double-stack_rail_transport#No...

Electrification is an aspect also, though I don't know if EU mixes passenger and freight as much as the US does (and also, more of the EU is relatively easy accessed by ocean going ships).

> Wikipedia has a list of some of the big remaining ones

That's a list of projects that are undergoing expansion from single-stack to double-stack, although that's not the main purpose of CREATE, and the Cross-Harbor Rail Tunnel is a perennially-proposed project to link NJ with Long Island that's unlikely to come to fruition. Furthermore, my understanding is that most of those projects are already completed; Wikipedia isn't always timely on updating these kinds of topics.

I say this as someone who would support it, but the Cross Harbor Freight Tunnel is pretty much vaporware.

It isn’t the only issue; apparently double stack has issues with third rail electrification, which is the norm on New York City area commuter rail, so even if you built the tunnel, a double stack train may not be able to go much further.