Making the Pitch
Let’s be direct (a very un-British thing for me to do).
If an American comes to Britain to pitch their new startup and ask for funding and partnership in the way that is normal in the US, that person will be viewed as arrogant and a braggard and will not be believed. If a Brit pitches in the US like they do in the UK, they will be perceived as lacking confidence and not believing in their product. This is a cultural issue that can kill your dreams upon landing.
Some things to remember when pitching are simple directness and clarity. I think the Yanks need to work on clarity, and the Brits need to work on directness. But both principles apply to both countries.