That would be a struggle.
AFAIK they are still using the 'mobile lounges' to transport international arrivals from the plane to immigration, so you need to wait for them to arrive, collect all the passengers then head to immigration.
Immigration at IAD can be a total pest with long waiting times. You like most probably will then need another transport to the other terminals for your onward departure.

However, massive improvements at IAD are underway, and perhaps someone else can help with current information ?