WP, The former - yes, the latter - I don't believe so.
The Springfield SAR-48 series rifles (Mine's a SAR-4800, meaning it's post-'98, pre-'94) were made in Brazil, probably by Imbel and imported, just like their 1911 clones, one of which I used to own.
Yours, being a SAR-48 meaning it's a pre-'89, so you don't need to worry about compliance parts, you can do whatever you dang well please with that rifle just so long as it doesn't violate the NFA. Me on the other hand... I'm stuck with one that I can only add U.S. parts to. At least it's 922(r) as-is and I don't need to add any more to it, however I can't take any away from it either.
If Springfield were to make their parts in the U.S. (receivers, barrels, fire control parts, lowers, gas systems, furniture) then yeah, I bet they could go right ahead and sell that rifle again in the U.S., but each rifle would likely cost over $2,000 a copy.