Good summary from The Post of where things currently stand with the NEC. Some other bits of the line's infrastructure up for potential renewal or replacement with alternatives including the B&P tunnel alternative under Baltimore which appears as 'shovel-ready' as things can get without actually having any budget to get started.
Obviously the NEC is in desperate need of investment, but old tunnels, etc are not unique to the US.
It appears that over the years there have been poor standards of maintainence. Now, I understand Sandy caused significant damage to the Hudson river tunnels, but it does seem like more consistent inspection and engineering work has to be done in general. There needs to be leadership who is willing to take the hit on inconveniencing travellers for periods of potentially months, in order to get on top of the maintainence backlog and carry out renewals. For example, I was significantly inconvenienced by the works at Derby station back in 2018, but now absolutely see the night and day difference in reliability and speed it has brought about.
The UK has done a fairly good job with lower levels of investment than our European neighbours and stop-start funding (especially for capital projects). Probably best to learn some lessons!
To me it seems speeding up and de-congesting the slow parts is a priority over speeding up the fast parts. Increasing a 20mph to a 40mph is a doubling in speed vs 12% from 160-180mph. Improvements should be made that offer the most cost effective journey time improvements for all passengers. That being said, I recognise that if the upgrades for 125-150 are just replacing some jointed track with welded rail, then absolutely go ahead, but getting any decent amount of the corridor to 186mph speeds seems better for marketing than service improvement. The UK does pretty well with 125mph, but we now have ridership and growth to support creating dedicated HSR anyway (HS1,2 & 3), and a network that is already being utilised to its fullest practical potential.