Depends how you earned the US bond income...
If it was 1099-INT Box 3 (Treasury Note interest or T-Bills usually) it will flow automatically to your state return as a subtraction as DaveF says.
Also if you had a MM fund which reported dividends in 1099-DIV Box1 there is an interview question after the 1099-DIV input screen whether any of it was US Gov interest and you enter the $ amount on the following screen, which will also flow to your state subtraction. You have to derive that amount based on % of US Gov provided by the fund company as "supplemental tax information", or in your 1099 statement in some cases, multiplied by the dividend received from that fund. Importing a 1099 does not figure this out you have to edit the 1099 and go thru the interview to make this adjustment.
You may also have 1099-OID Box 8 if you hold TIPS or STRIPS, that will also flow to state subtraction.
For all the above, check VA Form 760 line 7 or Schedule ADJ/CG line 4 for the total amount of subtraction is as you expect.
Lastly, If you held a discounted Treasury Note that reports "Accrued Market Discount" (the discount on the bond when you acquired it) as an adjustment to the gain/loss in Box 1f, TT will put that on your Schedule B as ordinary interest but it does not flow to state tax automatically. But we can get into that further if it applies.
