We’ve used a US TA to book the majority of our cruises (Celebrity, Royal and Princess). It’s only recently, since COVID, that I’ve been a little hesitant. Having said that, you need to price check on the cruise that you are considering as many European cruises may be cheaper over here than booking in the US. Additionally, many cruise lines are offering free/discounted flights if booked here and that may cancel out any of the reductions of booking in the US. Do a price comparison on both sides of the pond and see what the difference is,