I'm looking for a host family from any English speaking country.

One of the main reasons for the Au pair program is to improve or learn the language of the country you are going to. Your host family must speak a language different from yours. So if you speak English you can't be an Au pair for a host family that speaks English.

Look up the country information on the website to see which countries you can be an Au pair in.

Hope this helps!

While it's true, that learning and improving language skills is one reason for becoming an au pair, the other reason is to get to know the country and the culture, and this of course is possible for you in any English speaking country, as long as you fulfil the visa requirements. In your case especially the age restriction might keep you from becoming an au pair, as the au pair programs are mostly only for young adults of 30 (sometimes even 26) years or less.

Speaking the language of your host family at least to some extend is (in contrast to the answer given by Kudakwashe Mbirimi) even a pre-requisit to become an au pair in most countries!

What many countries forbid, is to have the same citizenship as your host family, so for example you couldn't become an au pair for a couple living in Germany, who holds passports from Zimbabwe - no matter which language(s) they speak.