That is a difficult question to answer without knowing a great deal about the entities, their owners, related parties, related party transactions, ownership attribution, etc.  Conducting a US trade/business and sourcing of US income has a number of exceptions beyond the obvious (see Code, Treasury Regs. and Treaty, if one).  Start with the instructions to Form 1120-F and then dive into the code, regs., etc.  Consider that: (i) FC will lose deductions after 18 mos.(?) and will be taxed on gross income if it fails to file and should have and (ii) filing a protective 1120-F with an 8833 taking (and explaining) a position of 'no permanent establishment' may make sense and eliminate some of the exposure for what otherwise might be the failure to file other information returns (e.g., 5472).  Good luck!

P.S.  No 1120-F in ProSeries tax package.