Can i use a global stamp for domestic mail

In the United States, the answer is generally no, you cannot use a global stamp for domestic mail. Here's why:

Domestic mail rates are typically lower than international rates, so you'll need to use a domestic stamp or a Forever Stamp (which is valid for domestic mail) to send mail within the United States.

However, there is an exception:

In summary, while you can't use a global stamp for domestic mail within the continental United States, you can use it for mail sent to U.S. territories or possessions.