I would leave aside the idea of staying or working in the US for now since mentioning it at your visa interview is automatic grounds for application dismissal (your goal is to study: focus on studying --whatever comes next… isn’t part of the student visa process.) you’ll be required to provide your social media handle(s) and that content too can be used against you.
Are both affordable?
Both will prepare you well for grad school, with a bit of a nudge for Lafayette.
You can attend either one and either enter a Master’s degree in Germany or in the US depending on what’s best for you at that point. FUBerlin will still be there in 4 years but attending Lafayette or Gettysburg is a once-in-a-lifetime opportunity.