Vastu science strives to be in harmony with environment.
The environment is more than what is obvious & visible. In fact the subtle environment is more impactful than the gross.
Yes, the vastu of entire house and surroundings have an impact.
And at the same time , you could harmonise the arrangements within the area of your control.
The room layout guidelines also suggest that the southwest area should be higher and heavier and your bed should be in that area witht head rest towards the south.
Karma is many more times powerful and spiritual practices do reduce the ill effects of all sorts.