Why my fed tax so high

We cannot see your tax return so we cannot tell you why you owe.   But an extension does not give you extra time to pay the tax that is due on April 18, 2022.   An extension only gives you extra time to file your Form 1040.   Tax due is supposed to be paid by the deadline in April.   You can ask for a payment plan with the IRS.

To apply for a payment plan with the IRS

Apply Online for a Payment Plan

No one in this user forum can see your tax return or your screen.  There were major tax law changes that began with the 2018 tax year that seem to continue to surprise some people.  Personal exemptions of over $4000 per person were removed beginning with 2018 returns.

 Was something different for 2021?  Did you have less income due to the pandemic?  Did you receive unemployment compensation?  If so, did you have tax withheld from it?

There are a lot of variables that affect your refund or tax due including how much you earned, how much tax you had withheld, your filing status, the number of dependents you claim, your deductions and credits, etc.  You may have lost Earned Income Credit or the Child Tax Credit— did a child turn 18?  If you received the EIC last year, remember that changes in the amount you earn have a big effect on the amount of EIC you can get. (Sometimes earning more money means less EIC)  Are you 65 or older ?  If so, your standard deduction is higher. Everyone has a higher standard deduction now so it is harder to use itemized deductions.

And of course, always check your own data entries, looking for errors such as misplaced decimals or extra zeros.

https://ttlc.intuit.com/questions/1901008-why-did-my-refund-go-down-compared-to-last-year-s

Print out 2020  and 2021 and compare them side by side to see what is different. 

https://www.postbulletin.com/news/business/tax-preparers-warn-your-refund-may-be-smaller-than-usual/article_2019b754-4d83-503e-ac96-17e0ffcde602.html

https://turbotax.intuit.com/tax-tips/tax-payments/video-why-would-i-owe-federal-taxes/L3VXudPiN