There's been a couple of confusing "non-facts" thrown around in this thread.
If you have an airspeed of 65kts and a 10kt headwind, you don't have a "55kt engine component and a 10kt wind component" that would suggest that your engine does not need to put out the same power to maintain that airspeed, this is false. Your engine is pulling you through the airmass and is giving you 65kts airspeed. The air happens to be travelling at 10kts across the GROUND in the opposite direction. Your 65kt airspeed translates to a 55kt ground speed.
Aircraft need AIRSPEED to fly, groundspeed is irrelevant (except for navigation).
Forget about jetstreams, they are a consistant airmass that your aircraft is travelling through. Where windshear comes into the equation is that it occurs when your aircraft moves from one airmass to another. Each airmass has diferent velocities and there will be a momentary change in the aircraft's AIRSPEED as it makes the transition.
The kind of thinking in some of the above posts is what leads people to believe that you will lose AIRSPEED if you turn from heading into wind, to heading down wind. So long as you are remaining in a stable airmass then your airspeed will remain stable, regardless of what direction you are flying relative to the airmass.