Air carrier landing Runway 7R at ANC was cleared to cross Runway 7L but then instructed to hold short after crossing the hold short line; ATC issued go around to landing aircraft.

Narrative

Landing ANC Runway 7R. Had requested; and received; clearance for a practice CAT3/HUD landing. There was moderate turbulence reported; and experienced; between 2;000 and 3;000. While being vectored for intercept; I heard ATC report our position to another aircraft who was cleared for a visual on 7L. They were staggered behind us. Due to the turbulence; my attention was on the approach and then later; the landing; so I lost situational awareness with the position of the other aircraft. We landed on Runway 7R; and while decelerating; trying to make taxiway G; I heard the tower controller clear us onto Golf and cross Runway 7L. The First Officer read back the clearance; and I verbalized it to him for confirmation. Immediately after that; there was a radio call to another aircraft which I disregarded because I was taxiing; but then heard our call sign; and told the First Officer; 'I think that was for us.' It was the tower controller instructing us to hold short; but we had already crossed the hold short line. We stopped; but were over the line by half a plane length. He then instructed the aircraft approaching Runway 7L to go around. They were still well down field; over the numbers approximately; but I couldn't yet see them as taxiway G is at an angle to that runway and I hadn't fully turned perpendicular. When we crossed; we queried the controller about our clearance; and he acknowledged that he'd cleared us to cross; and then said; 'That was my fault.' High workload; deceleration not as good as I was expecting which focused my attention on making a safe slowdown and then turnoff. When I heard our clearance to cross; I confirmed it; but should have stayed attuned to the other radio calls. Stopped the a/c but was already over the line. When we got to the gate; I called the tower cab; but all the supervisor had to say was that; yes we were cleared to cross; but then subsequently instructed to hold short; a call I did not hear. I think it's important for controllers to wait until the landing a/c has slowed enough; before issuing instructions to cross or hold short of a runway.