Tax Exempt interest (line 2a). The US return does not add that in, but Form 1116 does.
Social Security (lines 6a and 6b) - The US return only uses the taxable amount (line 6b), but Form 1116 uses the full amount (line 6a).
Capital gains (line 7). Did you sell multiple items, and any at a loss? Line 7 of the US return adds up the ones with gain, and subtracts the ones with losses. Form 1116 only adds up the ones with the gains.
