Use the Attribute manager and on the right hand side open the US template.
Select all the layers and layer combinations and 'OVERWRITE BY INDEX NUMBER' them to your INT file on the left side.
It may be better to purge any unused layers and layer combination on the left before you transfer the US ones in.
This is because when overwriting attributes by index, they will keep the same index numbers.
You will want to make sure that there are no old INT layers (and combinations) left behind after the overwrite.
i.e. if INT has a layer with index 23 and the US file does not, it will remain in your INT file.
You will then need to delete and replace this layer with something equivalent from the US layers (or simply delete it if there is nothing in it).
Overwriting by name will be useless as the names will all be different.
Appending will alter all the index numbers which may not be a good thing either.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11