There is a high likelihood that in a few years time US could lose a war against China.

I am assuming that such a war would be over Taiwan and would start either because of a blockade or a naval landing.

I think that a large portion of the US populace has grown completely complacent in relation to the Chinese threat, since they are used to United States fighting non-peer wars. They assume that China in 2025 or China in 2027, 2030 or 2035 is and will be the same China as in the late 90s to early 2000s, when China mostly was a place for manufacturing cheap, low quality products for western consumers. China today is either the leading or atleast major manufacturer in many advanced technologies, from robotics to electric vehicles to solar panels and wind turbines, computers, smart phones, semiconductors or ships.

First, China has massive production capacity. It is estimated that China is responsible for around a half of the global shipbuilding and that China has around 200-times the US shipbuilding capacity. If war were to begin, China could shift to producing military vessels, while US would far more struggle to do so. Second, China has been quickly catching up to the US in naval tehnology and seems to have advanced frigates for example, while for the past few decades US has been struggling to build frigates, latest example being the cancellation of the Constellation-programme. For example, China is currently building a Type 004 nuclear aircraft carrier, which could match US carriers in tonnage, while also have advanced tech such as Electromagnetic catapults. Same industrial capacity applies to other military equipment.

More importantly, China can concentrate all of it's military capacity in it's backyard, while US would have to fight a war an ocean away. In addition to their naval assets, China could use ballistic or hypersonic missiles, which China has far more than the US, to harass and potentially sink US carrier groups. China also would have access to large number of ground-based aircraft, including 5th gen stealth J-20s and in few years potentially even 6th gen fighter jets. It is assumed that China also could use it's massive ballistic missile reserves to damage or destroy US or it's allies airfields in the Pacific and South China sea region, which in practise could limit the amount of fighter jets US could bring to the region.

If I were to guess, Chinese morale would also be higher, since Chinese propaganda has been preparing for this exact possibility for decades. Also overwhelming majority of Chinese citizens see Taiwan as an integral part of China, so it would be easier to justify starting a war over the island than to at the moment war-weary americans.

At this exact moment I would still say that the US has the advantage alongside it's allies such as Japan or Australia, but the gap is closing especially on the naval front. US still largely has the technological advantage, but it is narrowing and is nowhere comparable for example to the one US had against Iraq in the 90s. US should not assume that they are invincible or that their enemies are incapable of adapting or learning, even if they may for now lack practical military experience. If US wants to win, it needs to get serious and significantly increase naval production capacity and maybe actually get some frigates built. US should also be ready to fight a conflict for years against an opponent who can outproduce and outman them, not an enemy that is to be underestimated.

I would also assume that initially China would suffer higher casualties, but due to the previously mentioned production capacity, China would also be far better suited to replace their losses. With current naval production US simply would be incapable of replacing it's losses on a short time frame. It should also be assumed that the Chinese are aware of this fact, so they very well may be ready to fight a prolonged war. China has tried to make itselt less reliant on the US for example with the belt and road initiative, oil pipe projects with various countries or trying to keep entire supply chains in China, from mining to refining to manufacturing.

In many ways in my opinion, US is similar to 1941 Japan in comparison to the US then (China in this case), nation with advanced military ships and competent pilots and quite advanced aircraft, but not the necessary industrial capacity to replace their losses in a larger conflict. Large reason for the allies eventual victory was the US incredible capability to produce everything from planes, trucks, rations, tanks, convoys, military vessels or aircraft at greater capacity than anybody else, to my knowledge more than all axis powers combined. Well now China more or less is in similar position to 1941 US.

One option of course would be not to fight, but that would de-facto mean US abandoning it's hegemony and more importantly, would leave the leading advanced semiconductor manufacturer under Chinese control, which could be further used to try economically influence the heavily tech-reliant US

Over the past few years, it feels like the global system has made one thing pretty clear that if you are a major power, using military force to take territory does not lead to consequences that actually stop you.

Russia invaded Ukraine and tried to annex it. Yes, there were sanctions and a lot of strong statements, but the war is still going on, trade routes adjusted, and Russia is still very much functioning.

The US openly talks about possible military action against Venezuela, and it is mostly treated as another geopolitical debate, not some red line that would “break the world order.”

Israel has effectively flattened Gaza with massive civilian casualties. The world argues about it, protests, and moves on. No one truly steps in to stop it.

Looking at all of this, I honestly do not see why China would think that invading Taiwan would be treated as some fundamentally different case.