Complex sentence: By the mid to late 1980s, the "Destroyer II" and "X-Series" lines were phased out in both the United States and Japan, however, the "X-Series" line continued in the United States market with other non-Destroyer models.
Split into simpler sentences: By the mid to late 1980s, the "Destroyer II" line was phased out both in the United States and in Japan. The "X-Series" models were also phased out of the United States market, however, the "X-Series" line continued with other non-Destroyer models.