On paper EUV relatively modest undertaking vs commercial aviation, EUV deeper integration vs commercial aviation breadth, but in terms of scale of effort for nation state coordination, EUV probably all things considered, easier to replicate because it has no regulatory slowdown, it's purely host country physics problem. Having enough talent and throwing it at problem x espionage x poaching talent x time will likely solve precision physics problem sooner than later. Vs commercial aviation which has complicated geopolitical/regulatory hurdles and magnitude more suppliers and scale. TLDR EUV has smaller organizational surface area for determined state to pursue through concentrating $$$, talent and effort. You can buy a ex ASML to bootstrap EUV development, much harder to get globe to buy COMAC without decades of airworthiness. There's a reason western analysts predict PRC EUV in 2030s (meanwhile PRC already beat prototype estimate timeline), but probably not realistic for global COMAC in same timeframe, and PRC been hammering at commercial aviation seriously long before EUV.
Of course, doing it "legally" is another question - someone in the US trying to replicate would likely run into patent and other issues.
But a top-secret Manhattan-style project done by the US or China? definitely doable, and if you add spy-shit in, perhaps even faster.
Either China will catch up on this or that particular technology will become obsolete. But it is certain that they won't stay behind forever (measured in a small number of decades at most).
What is far less certain is what ASML will be able to do at that time, i.e. if they will be able to progress significantly over the state-of-the-art of today, or they will reach a plateau.
Besides China, there is a renewed effort in Japan to become competitive again, so ASML may face in the future both Chinese and Japanese competitors.