The US arm force is created to engage and defeat China and Russia simultaneously. I would put my bets with the US in this encounter.
That was what everyone said during the Korean War. But we all know how that ended up for the Americans
China lost more soldiers but America was successfully kicked out of North Korea.
Germany had more sophisticated tanks than the Soviets in WW2, but the soviets had more cheaper tanks and outnumbered the advanced German tanks. The Soviets destroyed those advanced German tanks despite the Soviets losing far more tanks of their own than the Germans. Soviets achieved strategic victory.
In war, many things come into consideration. Things like weather conditions, logistics, tactics, strategies, ability to make your own weapons (and all components) in your own country, size of industry, speed of weapons production during war, money, access to natural resources, etc.
China has shown we are willing to endure massive casualties in order to achieve our strategic objectives of going to war.
Any war with China or Russia will take everything the US military has.
China might not be as technologically advanced as the US, but as the Korean War showed, being more technologically advanced doesn't guarantee you strategic victory.
Never underestimate the will of the People's Liberation Army. EVER!