I was actually thinking about this in terms of Twitch subscriptions. If an American pays $5 to subscribe, then the creator could easily end up seeing less than $1.20 from it.

First there's a ~20% VAT on it. $4 left. Twitch takes half of that - $2. The US takes another 0-24% from it. The local taxman takes another ~40%. You're roughly left with ~$1.

Kind of depressing when you look at it like that.

It’s highway robbery.

Can you deduct the US tax paid as a business expense?

It doesn't matter because your revenue is already reduced, so you can't deduct it again. For instance, if you originally earned $1000/month from youtube with zero expenses, for a profit of $1000/month that you have to pay taxes on. With youtube withholding 30%, your new revenue would be $700/month, for a profit of $700/month. You can't take your new revenue of $700/month, deduct the $300 tax as an expense, for a final profit of $400/month.

In the USA you can get a credit on your taxes for the amount of foreign tax paid, regardless of whether it was withheld or you paid it after he fact. This can eliminate the double taxation effect. In you example, let’s say you earned $1000 in a foreign country and paid $300 foreign tax. In the US you are taxed on the $1000, let’s say $400, but you can credit the $300 and only pay the incremental $100 of tax.

However America taxes world wide income, so it may be different in your country. You should probably ask a tax or accounting expert.