Complex sentence: The Tomahawk is now facing anti-cruise missile surface-to-air missile threats, and to counter these threats the U.S. is developing a successor to the Tomahawk called the Cruise Missile XR (Extended Range).
Split into simpler sentences: The Tomahawk is now facing anti-cruise missile surface-to-air missile threats. To counter this, the U.S. is developing a successor to the Tomahawk called the Cruise Missile XR (Extended Range).