Actually it’s 30% imported parts, through the entire Boeing fleet of aircraft. They got burned by outsourcing too much for the 787. That led to a 2 year delay in certification.
Every part for the 737 can be manufactured inside the US. Boeing claims to save a little money by using foreign companies for some parts. How much of that outsourcing is done purely for monetary purposes isn’t known. Some of the outsourcing is done for political backscratching reasons also.
EC
Hard to get exact numbers, but the list is extensive and includes complex, advanced systems that will take years to reshore to the US.
Fly-by-Wire Systems (France — Thales)
Autopilot & Flight Computers (France — Thales, Sweden — Saab)
Hydraulic Actuators (Germany — Liebherr)
Wing Leading Edges (UK — Spirit AeroSystems Scotland)
Horizontal Stabilizers (Italy — Leonardo)
Turbofan core, nacelles, fuel system, Fan & Fan Case - France (Safran)
High-pressure compressors - Germany (MTU Aero Engines)
Germany (Liebherr): Actuation systems
Turbine components and engine alloys - Japan (IHI Corp)
Gearbox components - Italy(Avio Aero)
Sensors & monitoring systems - United Kingdom(Meggitt)
Engine health monitoring systems - Canada (L3Harris)
Structural components - South Korea (Hanwha Aerospace)
Winglets & Composites (Japan — Mitsubishi, South Korea — KAI)
Seats (Germany — Recaro)
Galleys & Lavatories (France — Safran Cabin)
Overhead Bins (Mexico — C&D Zodiac)
Power Management (Switzerland — ABB)
Circuit Breakers (Ireland — Eaton)