Questions about taxes from USA income issued by Delaware llc or UK ltd

We are PC game makers. Our publisher is from USA-California and we are going invoice them for services. I have company in UK (ltd) and I want create new company in Delaware (offshore llc).



I have questions:

I want invoice the game from Delaware llc or UK ltd. Are there some federal, VAT, withholding.... taxes in USA?.



There are no such taxes from UK probably. Invoice will be without VAT. Will I pay taxes only in UK?



And what about Delaware llc? Can offshore company incorporated in Delaware have an income from USA? Must such company pay tax from this income? How much?



Does anybody has experience with this?