Those pre-employment credit checks will reveal the existence of IRS and state tax liens if you have not filed all required US returns or have unpaid taxes in the US. If the credit report shows unpaid US taxes, those offshore employers are choosing not to employ the US expatriate.
To avoid this problem, US expatriates need to keep current on current IRS tax filing requirements and file any past tax returns that are in arrears. If there are any IRS and state tax liens outstanding, it is best to pay them off or get assistance with the resolution of any liens you dispute. Let us know if you need help with past returns or resolving past tax liens.