It's a common misconception that a wheel misalignment or loose suspension parts can cause a vibration. This is false. Your vehicle’s alignment is the angle at which the wheels hit the road. It's not really possible for these angles to cause a vibration. If the alignment is way out, your tires will wear badly. This tire wear can get bad enough to make a vibration begin to develop, but understand that it's the tire that's causing the vibration at that point, not the alignment.
Loose suspension parts are another frequent suspect. People sometimes ask me if they have a loose ball joint or some other component causing the vibration they're feeling. The answer is always, "Loose suspension parts can aggravate a vibration, but they are not the cause of the vibration." Remember, vibrations are caused by rotating assembles, not necessarily loose parts. In fact, when a wheel is up to speed it acts like a gyroscope. This means that even with loose suspension parts, at speed, you may not notice the loose parts at all. Vibrations can actually create loose parts, sure, but that misses the point. Vibrations are almost always the result of something spinning that's out of balance. This imbalance is what causes the vibration. I've seen vehicles with very loose suspension parts drive smooth as glass down the road. I've also seen one wheel weight come off a wheel and it felt like the front end was about to fall apart.
The moral of the story is that you should put loose suspension parts and alignment at the very bottom of the list of things to check when dealing with a highway-speed vibration. They are very rarely, if ever, the cause of such things. Just to be thorough, I’m going to post a video here on how to inspect your suspension.