Here are some American slangs that I say and I hear other people

say
These are usually said by younger people like teenagers and young adults.

1.) Bomb is used when you say something is good.
For example : Starbucks caramel frappe is the bomb !
2.) Cheesin’ is used when you have a really big smile on your face.
For example: She was cheesin’ so hard at J-Hope when he called her pretty.
3.) Cap is basically another word for lying.
For example: No cap, I really like Jimin from BTS.

These are just a few examples of slang we use in America. You would sound very native if you use these words.