Open up the guts of the U.S. government — something President-elect Donald Trump hinted he will do — and what do you see?

A sprawling tangle of information technology services contracted out to private companies working on everything from Obamacare to immigration, air force bases and intelligence gathering. A look at NTT Data Corp. in Japan shows that some of the largest providers are owned by foreign companies, potentially putting them athwart Trump's "America first" brand of economic nationalism.

Some have been embedding themselves into the government for decades, operating typically through U.S. subsidiaries, often ones they acquired. Others write the code, provide consulting, develop strategies from offices in the U.S. and abroad, showing just how hard it may be to decide whether U.S. taxpayer dollars are really going to U.S. jobs.