First time I ever went to the 'states was back in 2005. En route to Florida with the family, we had to land in Philly and transfer to Orlando.. but because of adverse weather conditions (6 inches of snow!

baring in mind that this was late January) we were grounded for the next 12-ish hours.
My Dad decided to try and call up a hotel near the airport for us the hunker down for the evening and come back to the airport in the morning - but in the meantime, the airport itself was
full of Philly fans wanting to travel to Florida themselves for the Superbowl against the Patriots. Ended up chatting to and becoming friendly with a group of them, having never been exposed to NFL fans before (even though I obviously knew about it all beforehand) and I promised them that I'd root for the Eagles in the game. The cab driver on the way to the hotel was also a Philly local who asked us about Liverpool for the entire trip. In the short time we were there - I just got a really nice vibe about the people and they were technically my first proper introduction to America.
The following week in our villa in Kissimmee, I sat down and watched the Superbowl only having a passing knowledge of the rules of the game. Pats beat the Eagles 24-21 - but I became an Eagles fan (and NFL follower) from that point. I've dipped in and out of the sport over the years, but I'd always tried to look out for how the Eagles were doing regardless (they'd never won a Superbowl at that point). With how easy it is to follow it all these days though my fondest for the sport has grown a lot again in more recent years.