While the regular US tax filing deadline is April 15, if you are a US citizen residing abroad you are automatically entitled to a 2-month extension until June 15th without having to ask for one. By submitting Form 4868 to the IRS, you can ask for an extension until October 15th if you need more time.
It is crucial to remember that the extension is only available for tax return filing. Any tax debt must be paid in full by April 15th, beyond which point interest will start to accumulate on the tax payment that is due.