This "yankee bar" was a mandatory equipment for vehicles sold in the USA (also in Canada), perhaps their road legislation demanded bulkier bumpers or something. Renault's Plein Air must had originally been exported to Canada.
It should also have larger front headlamps and all red rear lights, among others, but these must have been replaced with standard items during the restoration.
Why did they keep the "yankee bar" is a mystery...
It can be fitted on a GTL, provided a) that you can find it (impossible, I think) and b) that you also find the complete fitting kit (ihe little support arms visible on the photo, the hinging mechanism etc).