I am booked to fly from MNL to IAD, with stops in Tokyo and LAX. My plans have changed, and I need to get to Dallas instead of IAD. Are there any negative implications to keeping my current flight, flying into LAX, and then just abandoning the last leg to IAD, and instead purchasing a new ticket from LAX to DFW?

Will they complain when I purchase the new ticket that it conflicts with my original flight? Anything else I should know? Will I have any trouble with Customs at LAX, or just tell them about the flight I arrived on and don't mention the next leg?

Thanks,
Steve