how does one cross the border with a mexican plated car or motorcycle? is it hard?

so i am a european expat living in mexico, but i would love to make a road trip in USA.

so i was wondering what the requirement/process is to get across the border with mexican plates.

-US insurance

-Identification/passport

-..........

what papers do i need more for the car/moto? some kind of temp import? or is that not needed if it will be just for a few weeks/months?