Snowball bush or European snowball, prefers a moist location and adapts to most soils. The large spherical flowers open apple green and then turn white.

It is grown in part shade or full sun. Is your bush getting enough sun. If it is leggy then maybe not. It needs at least 6 hours of direct sun. Maybe that's why its stems are weak.

It could probably use a pruning too. Prune it in early summer, after its flowering has finished. Clip the ends of the branches to remove spent flowers and thin out older stems to rejuvenate the shrub and keep it looking tidy.

"Snowball" bushes are species of Viburnums. However, several different species of Viburnums are known as snowballs - Chinese snowball (Viburnum macrocephalum), Japanese snowball (Viburnum plicatum), European snowball (Viburnum opulus 'Roseum') and fragrant snowball (Viburnum x carlecephalum). The one with the largest flowers is the Chinese but probably not hardy in your zone. I'd go with the European as well :-)

Here is a link that might be useful: Viburnum opulus 'Roseum'