It should not be too difficult to just book all your flights on one carrier that belongs to an airline alliance program (eg Star Alliance or OneWorld), with appropriate codeshares for either the domestic or the international flights. That way you have the whole thing on one ticket and will have protection against missed connection.

For instance, on OW you could book your transcon on AA and then transPacific on CX. On Star Alliance you could, theoretically, book the whole thing on UA. You don't say where you are leaving from or going to, so it's impossible to give more specific advice.