Comment by GTP

It really depends on which kind of data you're collecting. If you're collecting health related data that is linkable to the people it pertains to, the GDPR would prevent you from sharing that data with third parties without one of the admissible legal basis, the most common of which is the consent of the people whose data you collected. In the case of health data, maybe even USA laws would prevent you from sharing it.

Edit: it is now some time since I studied the GDPR, so I'm actually unsure if, for healt-related data, it can be used any legal basis other than consent. The reason being that health, together with a few other categories, has special protections.