I didn't say NVA suffer lower casualty, I'm saying you shouldn't omitted the sacrifice of South Vietnamese just to make US more badass, If US didn't get South Vietnamese help their casualties will be higher. Also many of that NVA casualties also the result of overwhelming US air superiority.
One big difference that war with China will have compared to these previous war is China has the means to strike US bases in the regions. China didn't have the means to attack US bases in Japan during Korean War, Vietnam didn't have the means to attack US bases in Thailand and Philippines during Vietnam War, Saddam didn't have the means to attack US bases in Saudi and Kuwait during Iraq war, Taliban didn't have the means to attack US bases in Pakistan and Uzbekistan during Afghan War. China has the largest constellation of spy satellites after US and they have thousands of ballistic missiles at their disposals that could reach as far as Guam. If they spot US stockpiling weapons and supplies in Japan, Korea, or Philippines that could be used against them do you think they won't preemptively strike it? if they spot US ships refueling and rearming in shipyards in Japan, Korea, or Philippines do you think the won't strike it? China has more resources at their disposal than any of previous US adversaries, and looking at the current events in Ukraine and Israel, keeping US busy by destabilizing their allies across the world is a good strategy. Let's say China decided to give weapons to Russia, Iran, North Korea, and every terror groups with axe to grinds against US, does US have the resources to deal with all of them at the same time?