All the action from the Pool B match in Brisbane.
Full-time: Scotland end both halves strongly against a plucky USA to secure their second win of the tournament but will have to lift their game for the French at the weekend. Scotland 39-15 USA
78 mins: Chris Paterson finishes a period of sustained pressure from Scotland to score the fifth try of the game. The same player converts.
Scotland 39-15 USA
75 mins: A woeful chip-kick from Mike Hercus is charged down by Glenn Metcalfe but Scotland fail to capitalise on the mistake. Kenny Logan replaces Gregor Townsend, with Chris Paterson moving to fly-half.
73 mins: USA are back to 15 men as Paul Emerick returns from the sin-bin. Bruce Douglas replaces Scotland no.1 Tom Smith.
71 mins: Gregor Townsend jinks his way over the try-line to earn Scotland a bonus point as the tired Americans allow Chris Paterson to dance past several slack challenges. Paterson misses the conversion.
Scotland 32-15 USA
67 mins: Great runs from Andy Henderson and Chris Paterson amount to nothing as poor back-up work again lets Scotland down.
65 mins: USA introduce Richard Liddington and Kimball Kjar.
64 mins: USA full-back Paul Emerick is yellow-carded for not letting go after a tackle.
63 mins: Glenn Metcalfe excites the crowd with a long run into USA territory but there is a lack of support for the Scottish full-back.
60 mins: USA win another penalty as the Scots become increasingly ragged and Mike Hercus reduces the deficit from in front of the posts.
Scotland 27-15 USA
59 mins: Scotland's squad skipper Bryan Redpath comes on to replace scrum-half Mike Blair.
56 mins: Scotland are given a penalty and Chris Paterson knocks over his side's first points of the second half.
Scotland 27-12 USA
53 mins: Scotland's Jon Petrie goes off with an apparent shoulder injury and Martin Leslie gets a taste of the action.
51 mins: Tom Smith makes an immediate impact with a powerful burst but the move breaks down after a forward pass from Simon Taylor.
50 mins: Scotland are back to 15 men as Tom Smith returns from the sin-bin. Ross Beattie also comes back into the fray as Bruce Douglas returns to the bench.
48 mins: Scottish scrum-half Mike Blair is penalised for obstruction at a scrum. Mike Hercus is on target with the kick.
Scotland 24-12 USA
46 mins: USA win two line-outs just a few yards from the Scottish try-line but are denied by some resolute defending.
44 mins: Scotland are penalised for a scrum-collapse but Mike Hercus' penalty hits the post and Phillip Eloff is penalised for a knock-on as he tries to collect and score.
42 mins: Ross Beattie is replaced by Bruce Douglas as 14-man Scotland look to soak up early second half pressure from USA. Jason Keyter comes on for USA's Kain Cross.
Half-time: After a nervous opening, three tries appear to have given Scotland control of the match. Scotland 24-9 USA
40 mins: Tom Smith is shown a yellow card for handling in the ruck as USA attack the Scottish try-line. Mike Hercus adds another three points.
Scotland 24-9 USA
38 mins: USA skipper Dave Hodges returns to the action.
37 mins: Prop Gavin Kerr charges down a USA clearance and shows great pace to get to the ball first and score Scotland's third try. Chris Paterson converts.
Scotland 24-6 USA
33 mins: USA are guilty of crossing in the midfield but Chris Paterson's long-range penalty drifts wide of the posts.
29 mins: USA skipper Dave Hodges has to leave the pitch with a nasty-looking head-cut.
24 mins: Simon Danielli scores his second try - crashing through three tackles - after some excellent footwork from Gregor Townsend saw the USA defence breached. Chris Paterson converts.
Scotland 17-6 USA
20 mins: A wonderful burst from Simon Danielli sees Scotland score the first try of the game after good work from Ross Beattie. Chris Paterson kicks the conversion from a tight angle.
Scotland 10-6 USA
16 mins: Scotland winger Chris Paterson is prevented from reaching his own kick near the USA try-line by the speedy Riaan van Zyl.
12 mins: Ross Beattie is penalised for a late tackle and the kick is moved on for back-chat from the Scots. Mike Hercus puts the USA ahead with the boot.
Scotland 3-6 USA
10 mins: Scotland respond with a strong period of pressure but a poor pass from Gregor Townsend sees a promising move break down.
7 mins: USA win a penalty, again for offside, after winning a Scottish line-out ball. Mike Hercus draws the underdogs level.
Scotland 3-3 USA
4 mins: USA are penalised for offside after a strong start from the Scots and Chris Paterson slots over a straightforward penalty.
Scotland 3-0 USA
1035 BST: Gregor Townsend kicks off a must-win match for Scotland.
Scotland have made nine changes for the match against the Eagles.
Most notably, Gregor Townsend comes in at fly-half and hooker Gordon Bulloch takes over the captaincy.
The Scots opened their campaign with a win over Japan and a good display is crucial ahead of their vital pool match against France at the weekend.
The USA have named an unchanged starting XV from the one that ran Fiji close in their opening game.
Scotland: G Metcalfe; S Danielli, A Craig, A Henderson, C Paterson; G Townsend, M Blair; T Smith, G Bulloch (capt), G Kerr, N Hines, S Grimes, R Beattie, S Taylor, J Petrie.
Replacements: R Russell, B Douglas, J White, M Leslie, B Redpath, B Hinshelwood, K Logan.
USA: P Emerick; D Fee, P Eloff, K Cross, R Van Zyl; M Hercus, K Dalzell; M MacDonald, K Khasigian, D Dorsey, A Parker, L Gross, K Schubert, D Hodges (capt), D Lyle.
Replacements: M Wyatt, R Liddington, J Gouws, O Fifita, K Kjar, J Keyter, L Wilfley.