Swinging the club back and into a position that sees the club pointing to the right of the target at the top of the backswing, or across the line, results in shots that have poor directional control.
From this across the line position, you can hit the ball out to the right if you swing down on the inside of the target line as your approach with the club head towards the ball will be too far inside the target line, producing a shot that flies to the right of target. Or, you will try to get the club head back into position and on to the target line by rotating your upper body excessively and throwing the club forwards, resulting in an action that makes the club head move over the top of your hands and on to the outside of the target line. To hit the ball, now you have to pull the club head back on to the target line, cutting across it as you do and the ball will fly left. Either way, there is very little chance of swinging the club head straight along the target line, to give yourself the chance of hitting a straight shot.
To improve your directional control, improve your club position at the top of your backswing. Displaying an across the line position at the top of your backswing is a product of an incorrect takeaway, mainly due to incorrect use of the wrists. As you take the club away from the ball, the club head should move along the target line and then rise upwards due to you hinging your wrist correctly.
If you stand in front of a wall or place an alignment pole behind you and slightly to the right, but parallel to your stance, as you take your golf club away from the ball it should not hit the wall or cross the alignment pole. If it does, you will now pick the club up and it will finish in a position that is across the line at the top of your backswing. Practice taking the club away so that it remains in front of the wall/alignment pole and parallel to it.
Use your wrists to hinge the club head upwards from the target line so that it rises to hand height but the shaft of the club remains parallel to your target line. This will now allow you to rotate into a much better backswing position which sees the club pointing parallel left of the target and allows you to gain much more accuracy with your golf shots.