True, but once people start talking about China's military being a threat to the US, that's going beyond comparing numbers and into what China can and cannot do with the capability it has (whatever that is). Currently, their military is a direct threat mostly to their nearest neighbours.
A Chinese threat to its neighbours is a threat to the USA, because of the USA's links with those countries. US-Japanese trade is over $200 billion. US-South Korean trade over $150 billion. Taiwan, $100 billion; Vietnam, $80 billion; Philippines, $30 billion. That's without going into all the other geopolitical interests at play - control of shipping lanes, resources, logistics etc. If Chinese influence envelops Japan, the USA's basically back all the way to the international date line.
In ten years, China will probably have at least one aircraft carrier similar in displacement to the latest US Navy vessels, and within twenty years, half a dozen. It will have caught up a lot of its technology shortfall, and be quite capable of menacing middle-size developing world nations across the globe itself at that point. Chances are it will, because there's no point building up a funky military without live testing and experience.
The USA is obliged to consider and plan for that reality.