If you are living in the US and meet the substantial presence test, then you are a US person for income tax purposes and must file a US resident tax return. In that case, there is no barrier to filing a joint return with your US spouse. A married couple may always file a joint return, even when one spouse is not employed, and joint returns almost always result in lower tax.
Since you seem to be asking about your withholding allowances at your job, if you will be filing a resident tax return, you follow the same rules as any other resident or citizen and use the same withholding form and you have the same rights to claim dependents.
If you do not live in the US, and do not meet the substantial presence test, and do not have a green card, then you are a nonresident alien, and you would file a nonresident alien tax return. Here, your options become more complicated. Rather than discuss those complicated options, it would be better to know a little bit more about your situation first.
