Exchanging files between USB drive and SD card

Can you help me understand the architectural requirements to be able to plug a USB drive into a Arduino USB Host Shield and then the system automatically exchanges specific files between them. So if the USB had a file named “hi.txt” and the SD had a file “bye.txt”, when I plug the USB drive in, it will write hi.txt to the SD and then write bye.txt to the USB drive.

Is this the right hardware configuration? Can you use a single Arduino?

USB Drive <-> USB Host Shield <-> Arduino <-> SD Shield <-> SD Card

Thanks in Advance!

Is this the right hardware configuration?

Yes.

Can you use a single Arduino?

As long as there are no pin conflicts for the shields, yes.

Reading from and writing to the SD card is easy. Reading from and writing to the USB device is not.