Harmful beer additives lead to hangover?

I was recently in England for a few weeks and did a normal tour around to the local pubs and on a few occions had a lot of beer. When I was over there, I did not get one hangover and when I am back home here in the states and drink that much beer, I feel like Im gonna die the next day. So what is the difference? I have been hearing a lot about harmful additives that American beer companies put in their beer to speed up fermentation. These chemicals can induce or intensify a hangover. Are there any beers here in the US without these additives?