You are going to send a whole team of star Rugby players in against a football team of NFL?
Just remember to bring one thing.
A good supply of bodybags.

So the US dominates every single sport, no other country can compete, NFL players are a different species to people from other countries

... Fuck off, if the same rugby players grew up playing NFL they would do fine.
I love NFL, but it will never be played seriously outside of US, it costs too much money to play and set up, football and rugby require a field, goals and a ball.... Not 50 sets of pads, helmets etc etc
Now they are no longer tackling head first the tackles could learn alot in regards to using the shoulder and wrapping the legs up as they do in rugby