It depends on your type of visa and whether you pass the substantial presence test. If you are considered a US resident for tax purposes, either because of your visa type or because of your length of residency, you must file US form 1040 tax return to report and pay tax on your worldwide income. In that case, you can take a text deduction for alimony paid in India assuming that it is alimony and not a property settlement.
However, if you are a nonresident, either because of your visa type or because you do not pass the substantial presence test, then you file a form 1040NR nonresident tax return, and you only pay income tax on your US income and you can only deduct US deductions.
