My family lives in UK but my 2 oldest children and myself have dual US/UK citizenship whereas my youngest is British only. We are travelling back to US and I want us to all travel on our British passports only - my family is struggling to be able to afford UK and US passports for myself and 2 oldest kids. I know all the advice is you must travel into US on US passports only - but I can't find any info on what actually happens if you don't? Is it illegal? Has anyone with US citizenship tried to enter or leave US on a different passport before? What happened?.... I can find any info online so any advice would be MUCH appreciated!!!!