Not little! Much bigger than native American hornets.

They likely arrived in containers from Japan or Korea. Unfortunately their favorite food is honeybees and they can easily wipe out a hive. Now honeybees are already stressed with diseases and parasites.

Modern agriculture is already stressful to honeybees: wildflower meadows are flattened and hit with herbicide to keep weeds out of paddocks sown to crops and the crops are increasingly huge areas of one crop—monoculture. This may mean honeybees do not get some nutrients they would get where there are multiple crops in a small area.

The real value of honeybees is the pollination services they provide. Some crops like wheat and tomatoes are pollinated by wind. Hardly any cherry trees can pollinate other cherry trees by wind and no other fruit tree can do it at all AFAIK.

In the US populations of other pollinators like native bumblebees are also being stressed with some now endangered.

So you say—that is the US, not here so irrelevant. We trade with Korea and Japan I believe, so not impossible we can have these monstrous murder hornets here! Hope containers keep being fumigated etc. AQIS does a vital job!

So plant some butterfly (and bee) attracting plants in your garden, good variety of them! Save the bees!