British English and American English are really different than each other as in vocabulary and usage. Do not think that because you British English is heavy so American English will be easy. For example, in American English the phrase “pass out” means to distribute or to lose consciousness, not the British English meaning of to graduate. Some words might even have completely opposite meanings. For example, “to table a measure” means stop planning for a while in US, not to commence discussion, and “public school” means a school operated by the city or state government, not a private school. The word “school” can be used to refer to colleges and universities, not just grammar school. In American English the abbreviation “s.o.” stands for “significant other”, a spouse or girlfriend/boyfriend, not sex offender.
British people following grammer rules but we can’t say that Americans very good at that. English usage among Americans will often differ from the grammar you learn from books. There are considerable dialectal variations across the country. Many Americans will not follow some of the prescriptive rules of grammar they learned in elementary school. Rules are often ignored. American English is an evolving language, not carved in stone.
When someone says “thank you”, the customary response is “you’re welcome”. “You’re welcome” doesn’t have the same meaning as in British English. Somebody who doesn’t speak English natively can understand British English easily but they can’t understand American English very clear.
Learning English is really easy when you have started but the question is which English you are gonna go for? American English or British English.
Whichever you choose English is worl wide language so you won’t be regret!