Potentially.

If it's had the correct number of foreign, countable parts replaced with US compliance parts, then it's not an illegal configuration. If it hasn't had sufficient countable parts replaced, then it is in an illegal configuration.

It gets more confusing when someone does a "cheapie" compliance makeover, by selling the rifle with a US-made, or partially US-made magazine, which technically brings the rifle into compliance, but only as long as it's never used with foreign-made magazines (the magazine itself contains three countable parts - body, floorplate, follower).

The most common parts to replace on a milled receiver rifle (with no muzzle brake/muzzle device) are the hammer/trigger/disconnector (3 parts), and a US-made pistol grip. On stamped receiver rifles, another part is needed, which is usually the gas piston. If a muzzle device is present, it needs to be US-made, as well, or another part (handguards, or buttstock are most common) needs to be US-made instead. Such a rifle can accept any magazines.