sd card

can you put two usa maps onto one sd card

Is this a query about adding Garmin suitable Openstreetmaps to an sd card?
If so, I expect you can if the .img maps fit and the names are different.
Be sure to have only one map enabled or you will get unexpected results unless one is just a transparent contour map to overlay another map.
You can use to edit the map names.
Card size is model dependent
For example:
And for outdoor models: