This is not like this! Legal foreign marriages are recognized by the US. A US citizen with a foreign spouse is therefore married for US tax purposes and is even allowed to file a joint tax return with the foreign spouse if you wish. By making this joint election, the foreign spouse enters the US tax system, which may not be a good idea if the foreign spouse has foreign income and assets. Filing a separate tax return may be a better option in that situation, but filing with “single” status is in no way a valid option. If you have eligible children dependents who have SSN or ITIN you can file as Head of Household. The IRS says
“If you are a U.S. citizen married to a nonresident alien, you may qualify to use the head of household tax rates. You are considered unmarried for head of household purposes if your spouse was a nonresident alien at any time during the year and you do not choose to treat your nonresident spouse as a resident alien”