When I lived there a place called "sports bar" near Piccadilly circus showed American football. It got PACKED on Saturdays though and was a bit tough to get a seat. Good luck!
If that doesn't work, you better check that you can get the station on your laptop because international rights don't carry for all networks and they'll black you out based on IP. You can either VPN to get a us IP address or subscribe to the international service if you're on a laptop. I also recommend getting an HDMI cable to hook to your hotel room TV.