Utter drivel.
During the early years of the post war when Europe was rebuilding then yeah, the USA footed the bill for out defence. In recent years though where the combine European military's are more than a match for the Russians the US forced stationed in Europe have had nothing to do with our defence and everything to do with your desire to be able to invade other parts of the planet. Say Trump decides to withdraw all force from Europe, then what? Won't affect us in the slightest but you will lose your European staging grounds, European medical hospitals, European airfields, European ports, you lose the whole lot. What happens when you decide to go romping around the middle east again? Well you now have to ask permission to start using all those facilities again. If you want to withdraw all your forces from Europe then feel free, it will have no impact on us. Every single war the USA has been involved in since WW2 has used European facilities to enable the military to function. You decide you don't want to be here? Fine, we decide we don't want such a backstabber using any of our military facilities. You want to invade the middle east, using Saudi Arabia again.
Also here is an interesting thing to note, the ONLY country that has used Article 6 to bring NATO allies into a conflict is *drum roll* the USA. So whilst you are getting on the bandwagon of whinging about how we are leeching off you, remember that since NATO was formed it's overwhelmingly been the USA dragging other countries into conflicts and it's only been the USA that have used the official NATO means to drag others it. When any other NATO members got into a conflict, the USA didn't lift a finger so stop selling this bullshit about how you are paying to protect us. The USA is acting as it always has done, in its own interests and nobody elses.